Clinical characteristics and treatment resource utilization among patients with substance use disorders: A comparative study of individuals who misuse pharmaceuticals and use illegal drugs
Fukuoka Prefectural Psychiatry Center Dazaifu Hospital, Fukuoka, Japan
Department of Drug Dependence Research, National Institute of Mental Health, National Center of Neurology and Psychiatry, Tokyo, Japan
Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
Department of Psychiatry, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
Abstract
Aim
In Japan, drug‐related issues are diverse, and the use of cannabis and pharmaceuticals is rising. This study aimed to clarify the differences in clinical characteristics and treatment resource utilization by drug type.
Methods
We analyzed data from 891 individuals from the 2024 Nationwide Psychiatric Hospital Survey, which comprised 368 who used methamphetamine or cannabis (illegal drug group) and 523 who used hypnotics, anti‐anxiety, or over‐the‐counter medications (pharmaceutical group). Clinical characteristics and use of treatment resources were compared by estimating risk differences and conducting logistic regression analyses.
Results
The pharmaceutical group had more young women, individuals who engaged in self‐harm, and those with comorbid psychiatric disorders than the illegal drug group. The illegal drug group had more males and individuals aged 30 years or older, with many meeting criteria for dependence syndrome. Moreover, they showed significantly higher use of outpatient group therapy, self‐help groups, and rehabilitation facilities. In the logistic regression analysis, the pharmaceutical group was independently associated with female sex, self‐harm, and comorbid psychiatric disorders, and were less likely to use outpatient group therapy but more likely to have a history of psychiatric hospitalization.
Conclusion
Illegal drug users more frequently accessed addiction‐specific services, whereas pharmaceutical users were more likely to receive psychiatric interventions. This suggests that pharmaceutical users have difficulty accessing traditional rehabilitation resources. Therefore, there is a need for a more comprehensive system that collaborates with general psychiatric care and offers flexible and tailored support.
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Keywords: drug‐related psychiatric disorders, illegal drugs, medical resources, non‐medical resources, pharmaceuticals
Article notes
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Revised 2025 Dec 7; Received 2025 Aug 11; Accepted 2025 Dec 15; Collection date 2025 Dec.
INTRODUCTION
The global landscape of substance use disorders has become increasingly complex. Although traditional concerns have focused on illegal drugs, such as methamphetamine, cocaine, and cannabis, there is a growing recognition of the harms associated with the misuse of prescription drugs, such as benzodiazepine receptor agonists and opioids. 1 , 2 For example, the opioid crisis in North America has highlighted the devastating impact of pharmaceutical drug misuse, with rising mortality due to overdose and increasing demand for treatment services. Similarly, European countries have reported growing trends in prescription drug dependence, particularly among adolescents and young adults. 3 , 4
Amid these global trends, the patterns of substance use in Japan have also undergone significant changes. Historically, the majority of arrests and incarcerations for drug‐related offenses in Japan have involved methamphetamine. However, the number of people arrested for violations of the Cannabis Control Act has increased annually over the past decade. In fact, in 2024, this number surpassed arrests for violations of the Stimulants Control Act. 5 During the 2010s, the abuse of new psychoactive substances (NPS) that circumvented legal restrictions became a major social concern in Japan. Although this issue abated following the implementation of stricter regulations that limited access to NPS, subsequent reports have suggested a transition to other illicit drugs and a growing concern regarding the misuse of over‐the‐counter (OTC) drugs. 6 , 7 In clinical settings, although opioid‐related problems remain relatively rare, issues related to the use of pharmaceuticals, such as benzodiazepine receptor agonists (e.g., sleep and anti‐anxiety medications) and OTC drugs, have seen a sharp rise. 8 Previous studies have indicated that sex, age group (youth or not), and the presence of comorbid psychiatric disorders can influence clinical characteristics and the challenges faced in treatment and recovery support. Furthermore, compared with illegal drug users, prescription drug users are more likely to be young women with comorbid psychiatric disorders. 9 , 10 Additionally, studies comparing methamphetamine users and hypnotic and anxiolytic users have shown differences in the proportions of International Classification of Diseases, 10th Revision (ICD‐10), sub‐diagnoses, such as dependence syndrome and psychotic disorders. Moreover, among all drug‐related psychiatric disorders, episodes of self‐harm and suicide attempts are disproportionately more frequent among cases involving hypnotics and anxiolytics. 11 It has also been reported that treatment frameworks originally developed for illegal drug users are not always suitable for prescription drug users, which may lead to greater difficulties in treatment. 9 , 12 In Japan, available treatment resources for substance use disorders include outpatient group therapy programs, such as the Serigaya Methamphetamine Relapse Prevention Program, 13 self‐help groups, such as Narcotics Anonymous (NA), and community‐based rehabilitation facilities, such as the Drug Addiction Rehabilitation Center (DARC). However, many of these resources were developed with the purpose of aiding illegal drug users. Therefore, their effectiveness for prescription drug users remains unclear.
Most studies to date have focused exclusively on either illegal drug users or prescription drug users, and few have directly compared the two groups. Consequently, a comprehensive and systematic analysis of differences in clinical characteristics and treatment resource utilization by type of substance used remains limited, particularly in the Japanese context.
The present study aimed to compare the clinical characteristics and treatment resource utilization of illegal drug users and prescription drug users within a unified framework. Using multivariable regression models, we further examined the associations between the type of substance used and patterns of treatment resource utilization. By systematically clarifying the current status of drug‐related psychiatric disorders in Japan, this study sought to provide a foundation for future development of clinical strategies and support systems.
METHODS
Nationwide psychiatric hospital survey
Since 1987, we have been conducting the biennial Nationwide Psychiatric Hospital (NPH) Survey, which targets all designated inpatient psychiatric medical facilities across Japan to investigate the state of drug‐related psychiatric disorders nationally. Each survey has consistently applied the same selection criteria for participating facilities and has been conducted during the same period, from September to October. This is the only complete enumeration survey in Japan that collects data on patients with drug‐related psychiatric disorders, and the results have served as crucial foundational data for drug abuse countermeasures in Japan. This study was a secondary analysis of data from the 2024 NPH Survey.
The NPH Survey period covered 2 months from September 2024 to October 2024 and targeted all hospitals in Japan with psychiatric inpatient wards. Survey subjects were patients who received either outpatient or inpatient treatment at participating facilities and were diagnosed under the ICD‐10 F1 category, “mental and behavioral disorders due to psychoactive substance use.” Cases of alcohol use alone were excluded; however, those who used alcohol in combination with another substance were included. Data collection was retrospective and based on information transcribed from medical records. Specifically, physicians at each participating facility extracted and recorded non‐identifiable information on a standardized survey form obtained from the medical records of patients with drug‐related psychiatric disorders who fulfilled the inclusion criteria. Completed forms were then mailed to the principal investigator, Dr. Toshihiko Matsumoto, for data aggregation. During the survey period, each participating facility posted a notice regarding the survey, with an opportunity for patients to opt out of study participation.
The survey items included age, sex, educational background, employment status, criminal history, drug use within the past year, type of “primary drug” currently used, ICD‐10 F1 subcategory diagnoses related to drug use, and comorbid psychiatric disorders. For each round of the survey, data collection was conducted using the same question wording and definitions for each item. The term “primary drug” referred to the psychoactive drug considered to be most clinically associated with the patient's current psychiatric symptoms. Attending physicians selected the primary drug from the following categories: methamphetamine, volatile solvents (e.g., toluene and paint thinner), cannabis, cocaine, heroin, 3,4‐methylenedioxymethamphetamine (MDMA), hallucinogens other than MDMA, new psychoactive substances, and prescribed sleep or anti‐anxiety medications (hereafter referred to as “sleep/anti‐anxiety medications.” The prescribed sleep/anti‐anxiety medications predominantly consisted of benzodiazepine receptor agonists, analgesics (prescribed non‐opioid drugs), analgesics (prescribed opioid drugs), OTC drugs (e.g., cough medicines, cold remedies, analgesics, and sleep medications), attention‐deficit hyperactivity disorder medications, other drugs, or polydrugs. For sleep/anti‐anxiety medications, analgesics, and OTC drugs, “use” was defined as drug use that exceeds medically and socially appropriate use; that is, when drug use had reached a level considered “abuse.” When multiple drugs were judged to have contributed equally to the psychiatric condition, “polydrug use” was selected.
Study subjects
The subjects were obtained from the 2024 NPH Survey data. Of the 1525 facilities surveyed, responses were obtained from 1098 facilities (72%). Cases were submitted from 221 facilities (14.5%), and a total of 2702 cases were included in the analysis according to the following criteria: informed consent was obtained, and there were no missing data for demographic variables or drug use information. Of the 2702 cases, 1481 cases were excluded because drug use had ceased for more than 1 year. From the remaining 1221 cases, we extracted those in whom the four most common primary substances were involved: methamphetamine, cannabis, hypnotics/anxiolytics, and OTC drugs. From this group, we extracted 277 methamphetamine cases, 91 cannabis cases, 246 sleep/anti‐anxiety medication cases, and 277 OTC drug cases, totaling 891 subjects who were included in the final analysis. Cases with missing data on any of the analyzed variables were excluded from the analyses (complete case analysis). We classified the 368 cases who used methamphetamine and cannabis as the “illegal drug group” and the 523 cases who used sleep/anti‐anxiety medications and OTC drugs as the “pharmaceutical group.” Although the nonmedical use of pharmaceuticals is not legally permitted in Japan, we classified substances according to whether the abused substance was an illegal or a pharmaceutical agent. Benzodiazepine receptor agonists are strictly regulated under the Narcotics and Psychotropics Control Law in Japan.
Variables
This study had two objectives: to clarify the differences in clinical characteristics between the illegal drug and pharmaceutical groups, and to examine the differences in the utilization of medical and non‐medical resources for treatment and rehabilitation support between the two groups. Based on these objectives, we defined the following variables.
For clinical characteristics, we selected independent variables with reference to previous studies and the results of the two‐group comparison: sex, age group (10–29 years/≥ 30 years), history of self‐harm or suicide attempt, presence of ICD‐10 F1x.2 dependence syndrome, and presence of comorbid psychiatric disorders. Given that ICD‐10 F1x.1 harmful use is mutually exclusive of F1x.2 dependence syndrome, we excluded this sub‐diagnosis from the analysis. Regarding the treatment and rehabilitation resources, variables were categorized into medical and non‐medical resources to reflect services that are commonly available to patients with drug‐related psychiatric disorders in Japan. As indicators of medical resource utilization, “experience of participation in outpatient group therapy for addiction” and “history of psychiatric hospitalization due to drug‐related issues” were selected as items corresponding to reimbursable medical service categories (i.e., group therapy for addiction and additional inpatient medical management fees for drug dependence) related to drug‐related psychiatric disorders. For indicators of non‐medical resources, we extracted information on variables such as “experience of participation in self‐help groups” (e.g., NA), which are essential components of community support for individuals with substance use disorders, and “experience in utilizing private addiction rehabilitation facilities” (e.g., DARC).
Statistical analysis
To compare the clinical characteristics and treatment resource utilization between the pharmaceutical and illegal drug groups, we calculated risk differences (RDs) for each item. A difference of 5% or greater was considered clinically meaningful. Risk differences (RDs) and 95% confidence intervals (CI) were calculated using the Newcombe method for differences in proportions. RDs were calculated as the proportion in the pharmaceutical group minus that in the illegal drug group. RDs were presented as percentage points (%). Logistic regression analysis was then performed to identify factors associated with the type of substance used (dependent variable: pharmaceutical = 1, illegal drug = 0). Models were built in a stepwise manner: Model 1 comprised demographic characteristics (i.e., sex and age group); Model 2 additionally comprised psychiatric characteristics (i.e., history of self‐harm or suicide attempt, diagnosis of dependence syndrome, and presence of comorbid psychiatric disorders); and Model 3 further consisted of treatment‐ and recovery‐related characteristics (i.e., participation in self‐help groups, participation in outpatient group therapy, history of psychiatric hospitalization due to drug problems, and use of private rehabilitation facilities). Odds ratios (ORs) were calculated for each model. To assess the robustness of the findings, we also conducted sensitivity analyses stratified by sex, age group (10–29 years vs. ≥30 years), and presence or absence of comorbid psychiatric disorders. The direction and magnitude of associations remained consistent across strata. All statistical analyses were performed using IBM SPSS Statistics, version 25.0 (IBM Corp.), with a two‐tailed significance level of 5%.
Ethical considerations
This study was conducted with the approval of the Ethics Committee of the National Center of Neurology and Psychiatry (approval number: A2024‐041).
RESULTS
Comparison of clinical characteristics between the pharmaceutical and illegal drug groups
The results are summarized in Table 1. There were more women in the pharmaceutical group than in the illegal drug group (66.2% vs 21.2%, RD = 45.0%, 95% CI: 39.2–50.8). Younger individuals (aged < 30 years) were also more prevalent in the pharmaceutical group (42.1% vs 23.1%, RD = 19.0%, 95% CI: 13.0–25.0) than in the illegal drug group. A history of self‐harm or suicide attempt was reported more frequently in the pharmaceutical group (53.2% vs 12.0%, RD = 41.2%, 95% CI: 35.8–46.6).
| Primary drug of abuse | ||||||
|---|---|---|---|---|---|---|
| Pharmaceutical group | Illegal drug group | |||||
| N = 523 | N = 368 | RD | 95% CI | |||
| % | % | lower | upper | |||
| Sex (Female) | 66.2 | 21.2 | 45.0 | 39.2 | 50.8 | |
| Current age group (10–29 years) | 42.1 | 23.1 | 19.0 | 13.0 | 25.0 | |
| Current alcohol‐related problems | 22.2 | 15.8 | 6.4 | 1.2 | 11.6 | |
| Experience of deliberate self‐harm or suicide attempt within the past year | 53.2 | 12.0 | 41.2 | 35.8 | 46.6 | |
| Diagnoses related to drug use (ICD‐10 F1 subcategory diagnoses) | F1x.0 Acute intoxication | 13.2 | 2.7 | 10.5 | 7.2 | 13.8 |
| F1x.1 Harmful use | 33.3 | 15.2 | 18.1 | 12.6 | 23.6 | |
| F1x.2 Dependence syndrome | 69.0 | 82.1 | −13.1 | −18.7 | −7.5 | |
| F1x.3 Withdrawal state | 3.8 | 4.9 | −1.1 | −3.8 | 1.6 | |
| F1x.4 Withdrawal state with delirium | 2.5 | 3.0 | −0.5 | −2.7 | 1.7 | |
| F1x.5 Psychotic disorder | 1.9 | 19.8 | −17.9 | −22.1 | −13.7 | |
| F1x.6 Amnesic syndrome | 1.7 | 0.3 | 1.4 | 0.2 | 2.6 | |
| F1x.7 Residual and late‐onset psychotic disorder | 0.6 | 11.4 | −10.8 | −14.1 | −7.5 | |
| F1x.8 Other mental and behavioral disorders | 0.6 | 0.0 | 0.6 | −0.1 | 1.3 | |
| Presence and type of comorbid psychiatric disorders (based on ICD‐10 major categories) | Any comorbid psychiatric disorder | 84.3 | 53.8 | 30.5 | 24.5 | 36.5 |
| F0 Organic, including symptomatic, mental disorders | 1.9 | 0.8 | 1.1 | −0.4 | 2.6 | |
| F2 Schizophrenia, schizotypal and delusional disorders | 7.6 | 10.3 | −2.7 | −6.5 | 1.1 | |
| F3 Mood (affective) disorders | 31.2 | 19.6 | 11.6 | 5.9 | 17.3 | |
| F4 Neurotic, stress‐related and somatoform disorders | 35.4 | 17.7 | 17.7 | 12.0 | 23.4 | |
| F5 Behavioral syndromes associated with physiological disturbances and physical factors | 5.0 | 1.4 | 3.6 | 1.4 | 5.8 | |
| F6 Disorders of adult personality and behavior | 14.1 | 7.6 | 6.5 | 2.5 | 10.5 | |
| F7 Intellectual disabilities | 6.9 | 5.4 | 1.5 | −1.7 | 4.7 | |
| F8 Disorders of psychological development | 14.3 | 3.5 | 10.8 | 7.3 | 14.3 | |
| F9 Behavioral and emotional disorders with onset usually occurring in childhood and adolescence | 9.8 | 13.6 | −3.8 | −8.1 | 0.5 | |
| Experience in utilizing resources for treatment and recovery | Experience of participation in outpatient group therapy for addiction | 29.3 | 54.1 | −24.8 | −31.2 | −18.4 |
| Experience of psychiatric hospitalization due to drug‐related issues | 59.5 | 50.3 | 9.2 | 2.6 | 15.8 | |
| Experience of participation in self‐help groups for drug addiction | 21.8 | 39.9 | −18.1 | −24.2 | −12.0 | |
| Experience in utilizing private addiction rehabilitation facilities | 9.2 | 24.2 | −15.0 | −20.0 | −10.0 | |
Regarding ICD‐10 sub‐diagnoses, acute intoxication (F1x.0: 13.2% vs 2.7%, RD = 10.5%, 95% CI: 7.2–13.8) and harmful use (F1x.1: 33.3% vs 15.2%, RD = 18.1%, 95% CI: 12.6–23.6) were more frequent in the pharmaceutical group, whereas dependence syndrome (F1x.2: 69% vs 82.1%, RD = −13.1%, 95% CI: −18.7 – −7.5), psychotic disorder (F1x.5: 1.9% vs 19.8%, RD = −17.9%, 95% CI: −22.1 to −13.7), and residual and late‐onset psychotic disorder (F1x.7: 0.6% vs 11.4%, RD = −10.8%, 95% CI: −14.1 to −7.5) were more common in the illegal drug group.
Comorbid psychiatric disorders were more common in the pharmaceutical group (84.3% vs 53.8%, RD = 30.5%, 95% CI: 24.5–36.5) than in the illegal drug group. Specifically, mood disorders (F3: 31.2% vs 19.6%, RD = 11.6%, 95% CI: 5.9–17.3), neurotic disorders (F4: 35.4% vs 17.7%, RD = 17.7%, 95% CI: 12.0–23.4), disorders of adult personality and behavior (F6: 14.1% vs 7.6%, RD = 6.5%, 95% CI: 2.5–10.5), and disorders of psychological development (F8: 14.3% vs 3.5%, RD = 10.8%, 95% CI: 7.3–14.3) were more frequent in the pharmaceutical group than in the illegal drug group.
In terms of treatment and rehabilitation resources, participation in outpatient group therapy for addiction (29.3% vs 54.1%, RD = −24.8%, 95% CI: −31.2 to −18.4), attendance at self‐help groups (21.8% vs 39.9%, RD = −18.1%, 95% CI: −24.2 to −12.0), and use of private rehabilitation facilities (9.2% vs 24.2%, RD = −15.0%, 95% CI: −20.0 to −10.0) were more frequent in the illegal drug group than in the pharmaceutical group. In contrast, psychiatric hospitalization due to drug‐related problems was more common in the pharmaceutical group (59.5% vs 50.3%, RD = 9.2%, 95% CI: 2.6–15.8) than in the illegal drug group.
Factors influencing the choice of treatment and recovery support
Results of each model are provided in Table 2. In Model 3, being in the pharmaceutical group was significantly associated with female sex (OR = 3.33, 95% CI: 2.34–4.73, p < 0.001), a history of self‐harm or suicide attempt in the past year (OR = 4.17, 95% CI: 2.74–6.34, p < 0.001), and comorbid psychiatric disorders (OR = 2.31, 95% CI: 1.61–3.32, p < 0.001). Participation in outpatient group therapy for addiction was less common (OR = 0.51, 95% CI: 0.35–0.75, p = 0.001), whereas psychiatric hospitalization was more common (OR = 1.57, 95% CI: 1.11–2.24, p = 0.012) in the pharmaceutical group than in the illegal drug group. Attendance at self‐help groups and use of private rehabilitation facilities were not significantly associated in Model 3 (OR = 0.66, 95% CI: 0.41–1.05, p = 0.076; OR = 0.85, 95% CI: 0.50–1.46, p = 0.56, respectively).
| Model１ | Model２ | Model３ | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| OR | 95% CI | p | OR | 95% CI | p | OR | 95% CI | p | ||||
| lower | upper | lower | upper | lower | upper | |||||||
| Female (ref: male) | 6.659 | 4.873 | 9.101 | <0.001 | 3.780 | 2.691 | 5.310 | <0.001 | 3.326 | 2.337 | 4.733 | <0.001 |
| Age 10–29 years (ref: ≥30 years) | 1.789 | 1.287 | 2.485 | 0.001 | 1.193 | 0.818 | 1.739 | 0.360 | 1.110 | 0.752 | 1.637 | 0.599 |
| Self‐harm or suicide attempt in the past year (ref: none) | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | 4.174 | 2.779 | 6.270 | <0.001 | 4.166 | 2.739 | 6.337 | <0.001 |
| F1x.2 dependence syndrome applicable (ref: not applicable) | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | 0.687 | 0.467 | 1.012 | 0.057 | 0.842 | 0.563 | 1.259 | 0.403 |
| Other comorbid psychiatric disorders (ref: absent) | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | 2.432 | 1.709 | 3.460 | <0.001 | 2.311 | 1.608 | 3.321 | <0.001 |
| Participation in outpatient group therapy (ref: none) | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | 0.509 | 0.348 | 0.746 | 0.001 |
| Psychiatric hospitalization (ref: none) | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | 1.572 | 1.105 | 2.236 | 0.012 |
| Participation in self‐help group (ref: none) | 0.657 | 0.413 | 1.046 | 0.076 | ||||||||
| Use of private rehabilitation facility (ref: none) | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | ‐‐‐ | 0.851 | 0.497 | 1.457 | 0.557 |
DISCUSSION
Differences in clinical characteristics between the pharmaceutical and illegal drug groups
The comparison between the two groups showed that the pharmaceutical group comprised a greater proportion of young women, which may represent a population with higher psychological vulnerability. Specifically, this group was characterized by a higher tendency toward polysubstance use (including alcohol), more frequent episodes of self‐harm, and a higher prevalence of comorbid psychiatric disorders. These findings are consistent with previous studies reporting similar trends and associations between emotional problems and self‐destructive behaviors. 14 , 15 , 16 For example, suicidal behavior is linked to actions of self‐harm and intentional overdose of psychotropic medications. 17 Additionally, a notable proportion of the pharmaceutical group met criteria for “harmful use” rather than dependence syndrome, which may reflect the younger age of this group and thus a shorter duration of drug use, suggestive of milder forms of substance use disorders. Moreover, the patterns of drug use in this group may be less habitual and more episodic or intermittent, characteristic of self‐destructive behavior. The individuals in the pharmaceutical group were also more likely to seek crisis intervention services for broader mental health issues, such as psychiatric inpatient care, but were less likely to access addiction‐specific medical and non‐medical resources, such as outpatient group therapy for addiction, self‐help groups, and private addiction rehabilitation facilities.
In contrast, the illegal drug group comprised more men and older individuals, with higher rates of diagnoses for dependence syndrome and psychotic disorders. The greater prevalence of dependence syndrome in this group may be attributed to prolonged, habitual drug use associated with older age. The higher prevalence of psychotic disorders in the illegal drug group is consistent with well‐documented pharmacological effects of stimulants and cannabis. 18 , 19 Additionally, the illegal drug group made greater use of addiction‐specific medical and non‐medical resources, such as outpatient group therapy, self‐help groups, and private addiction rehabilitation facilities, than the pharmaceutical group. This pattern suggests that the illegal drug group is better aligned with the conventional resource framework developed for community‐based support for individuals with substance use disorders.
The multivariate logistic regression analysis confirmed that female sex, a history of self‐harm or suicide attempt, and comorbid psychiatric disorders were consistently and independently associated with the use of prescription drugs, even after adjusting for demographic factors, diagnostic categories of dependence, and use of treatment resources. This finding strongly suggests that the pharmaceutical users are predominantly young women with underlying self‐destructive behaviors and psychiatric comorbidities. This highlights the need to emphasize clinical indicators beyond the type of substance (i.e., self‐harm risk, psychiatric comorbidities, and sex) when developing interventions and support strategies.
Differences in the utilization of medical and non‐medical resources
With regard to the use of treatment resources, we showed that the pharmaceutical group had more frequent psychiatric hospitalizations than the illegal drug group; however, participation in outpatient group therapy for addiction and self‐help groups and private rehabilitation facility use were less common. In contrast, the illegal drug group more frequently utilized addiction‐specific medical and non‐medical resources than the pharmaceutical group, which suggested a higher affinity for community‐based support systems for addiction.
The multivariate analysis confirmed that participation in outpatient group therapy was significantly less common in the pharmaceutical group, whereas psychiatric hospitalization was significantly more common. This pattern indicates that the pharmaceutical group tended to rely more on crisis‐oriented resources that address psychiatric symptoms and self‐harm risk than on addiction‐specific treatment. The differences in self‐help group attendance and private rehabilitation facility use did not remain significant after adjustment, which suggested that the differences observed in the bivariate analysis can be explained by other factors. Previous studies have noted that the presence of comorbid psychiatric disorders limits the suitability of group therapy for addiction. 20 , 21 Outpatient group therapy is more targeted for patients whose psychiatric symptoms are relatively stable and who can focus on addiction‐specific treatment. In contrast, given the high rates of self‐harm and comorbid disorders, psychiatric hospitalization functions more as an intervention for general crises, such as life disruption and suicidal behavior, rather than as a treatment specifically for substance dependence.
Taken together, these findings suggest that treatment and support for substance use disorders should be structured as a hybrid model—anchored on addiction‐specific medical and non‐medical resources—while incorporating non‐specific crisis interventions, such as psychiatric hospitalization when necessary.
The unique challenges of pharmaceutical use among women and implications for future support system development
Historically, methamphetamine use has been the primary focus of addiction treatment in Japan, with the majority of patients being middle‐aged men. Both medical and non‐medical resources for addiction treatment have been developed with consideration of a relatively homogeneous population of “middle‐aged, male methamphetamine users.” Consequently, individuals characterized as “young, female pharmaceutical users” constitute a minority within existing treatment resources and thus may not perceive these environments as safe or supportive.
The combination of characteristics identified in this study—“young, female pharmaceutical users”—is not merely a demographic pattern but may also reflect differences in motives for substance use and patterns of misuse. Prior research has shown that women, compared with men, more frequently present with comorbid psychiatric disorders and tend to use substances for self‐medicating purposes, such as alleviating interpersonal stress, depressive symptoms, or anxiety. 22 , 23 Unlike illegal drugs, pharmaceuticals are often used in the context of suicide attempts or other self‐harming behaviors.
When women seek treatment or support, they often face constraints related to stigma and to social roles such as family responsibilities, childcare, and employment, which can compound the difficulty of accessing appropriate care. 23 In Japan, strong gender role expectations—such as the notion that “women must remain composed and responsible”—persist, and women with substance‐related problems may be more likely to conceal their difficulties due to feelings of shame or beliefs that they are personally to blame. 22 Women are more prone to treatment dropout than men owing to various factors, such as comorbid mental health disorders and greater social vulnerability; moreover, they may be less adaptable to male‐centric treatment settings. 14 , 15 Previous studies have demonstrated that increasing and tailoring treatment options for women enhances opportunities for recovery. 24 , 25 Therefore, in the future, it is essential to expand resources that specifically target populations characterized by the attributes of “female, young, and prescription drug user.”
Additionally, many individuals consistent with the profile of “female, young, and pharmaceutical user” exhibit broad self‐destructive tendencies and high rates of comorbid psychiatric disorders, which lead to frequent psychiatric hospitalizations as non‐specific crisis interventions. In Japan, although recent policy efforts by the Ministry of Health, Labour and Welfare have focused on expanding specialized drug addiction treatment facilities, what may now be required is not merely the expansion of specialized drug addiction treatment facilities, but rather, the expansion of general psychiatric institutions that do not hesitate to treat patients with drug‐related issues.
Several limitations of our study must be acknowledged. First, the representativeness of the subjects may be limited. Because we focused exclusively on patients receiving treatment in psychiatric hospitals with inpatient facilities, our sample does not reflect the experiences of patients with drug‐related disorders treated in psychiatric clinics or general hospitals without psychiatric wards. Furthermore, our findings cannot be applied directly to all medical or non‐medical support settings in the community. Second, the validity of the variables used to assess the use of medical and non‐medical resources is limited. Although the reported experiences are likely to reflect a certain degree of alignment between the physician's judgment of necessity and the patient's willingness to utilize the resources, they may not indicate the effectiveness of the interventions. Third, there are inherent limitations in the data collected. Our data were collected via retrospective chart reviews of patients with drug‐related disorders by the treating physicians at each participating facility. As such, there is likely variability in clinical judgments and evaluations among physicians. Moreover, the information collected was limited and did not cover other potentially important variables. Additionally, our data may have self‐report bias regarding patients in clinical settings. The substance categories analyzed reflect clinical documentation and local testing capacities; consequently, some exposures (e.g., etomidate, vaping‐related toxicity, ketamine, and certain NPS) may be under‐captured. Caution is warranted when generalizing to jurisdictions with different surveillance and supply landscapes. The initiation period (September–October 2024) may coincide with time‐specific social or supply dynamics, potentially influencing case mix. Future follow‐up studies across longer windows are needed to evaluate external validity. Both the pharmaceutical and illegal drug groups may have comprised individuals who primarily used one type of substance but also had a history of using another drug type (e.g., those who primarily used pharmaceuticals but also occasionally used illegal drugs, and vice versa). However, because of the nature of the survey data, such cases could not be identified or separated in the analysis. Nevertheless, despite these limitations, our study provides important evidence highlighting the need for more nuanced and drug‐specific support strategies. Our findings offer a meaningful contribution to both clinical practice and community‐based support systems.
CONCLUSION
This study of clinical data from the 2024 NPH survey represents a large‐scale comparative analysis of prescription drug and illegal drug users within the same framework. Our findings demonstrated that being female, engaging in self‐harm or suicidal behavior within the past year, and having comorbid psychiatric disorders were more frequent in individuals who used prescription drugs than those who used illegal drugs. In terms of treatment resource utilization, illegal drug users were more closely aligned with conventional addiction recovery resources, such as outpatient group therapy, self‐help groups, and private rehabilitation facilities, whereas prescription drug users required psychiatric hospitalization as a form of crisis intervention more often than addiction‐specific services.
Our results indicate that, in addition to maintaining and strengthening addiction‐specific resources, enhancing the crisis management capacity of general psychiatric care and developing support programs tailored to the needs of prescription drug users are urgent priorities. The present findings underscore the importance of building a treatment system in which general psychiatric care and addiction‐specific services work in tandem, rather than simply expanding addiction‐specific resources, particularly given the growing concern around prescription drug misuse. Further longitudinal and intervention studies will be essential to clarify the types of support that are most effective in improving outcomes for prescription drug users.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interest.
ETHICS APPROVAL STATEMENT
This study was approved by the Ethical Review Committee of the National Center of Neurology and Psychiatry (approval number: A2024‐041).
PATIENT CONSENT STATEMENT
N/A.
CLINICAL TRIAL REGISTRATION
N/A.
ACKNOWLEDGMENTS
This study was supported by the Health Labour Research Grant from the Ministry of Health, Labour and Welfare, Research on Pharmaceutical and Medical Regulatory Science (Principal Investigator, Takuya Shimane; grant number, 23KC2006). We thank Sarina Iwabuchi, PhD, from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.
Untitled section
Usami T, Matsumoto T, Okita K, Nakao T, Shimane T. Clinical characteristics and treatment resource utilization among patients with substance use disorders: a comparative study of individuals who misuse pharmaceuticals and use illegal drugs. Psychiatry Clin Neurosci Rep. 2025;4:e70277. 10.1002/pcn5.70277
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are openly available. Raw data can be accessed by contacting the corresponding author. Before the data are used, approval for the secondary use of the data must be obtained from the Ethical Review Committee of the National Center of Neurology and Psychiatry.
REFERENCES
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Associated Data
Data Availability Statement
The data that support the findings of this study are openly available. Raw data can be accessed by contacting the corresponding author. Before the data are used, approval for the secondary use of the data must be obtained from the Ethical Review Committee of the National Center of Neurology and Psychiatry.