The main objective of Internet surveys investigating drug use behavior is to obtain valid and accurate measures of drug use in the population [66], and in our study, to obtain information on the personal and social consequences of drug use. Tools that use the Internet as an effective communication channel are an alternative for addressing the global problem of substance abuse, as this tends to be underreported [67]. A large number of studies conducted in recent decades have quite clearly underlined that self-administered questionnaires are more appropriate than other modes of data collection for collecting reports on sensitive behaviors such as this one [66,68]. Indeed, responses to self-administered questionnaires, whether completed with pen and paper or via a laptop computer, appear more reliable, and are particularly suitable for reporting behaviors that may compromise the respondent in some way, such as intimate or painful feelings, or illegal behaviors [69,70]. This could be attributed to the absence of a direct, identifiable witness, which therefore ensures the respondent’s anonymity and greater freedom of expression on personal topics such as this [71].

A large percentage (almost 80%) of Spanish families have an Internet connection, and 64.3% of the population uses the Internet on a daily basis [72] making it a crucial tool for population-based surveys as in the present study.

Our study showed that among the personal consequences of substance use, the item with the largest percentage of positive answers referred to forgetting personal experiences during use: “Do you ever FORGET things you did while using alcohol or drugs?”. This result is supported by the well-known effects of substance abuse on the neurophysiology of brain circuits related to memory, such as those involving the hippocampus [73,74,75,76]. Study in humans have shown that marijuana use alters multiple brain functions, including memory, as shown by the deficit in working and short-term memory related to its use [77]. Cannabis users showed poorer learning and memory than tobacco users, suggesting an effect of long-term cannabis use on memory despite short-term abstinence [78,79]. With respect to the effects of alcohol exposure on cognition, at higher doses it affects the performance of cognitive tasks that depend on the hippocampus, whereas at low doses it has no effect or even facilitates working memory when performing certain tasks [76]. Among the personal consequences, the item “Do you ever use alcohol or drugs to RELAX, feel better about yourself, or fit in? “ is the second most rated in our study. This use could be influenced by social culture, since some substances such as marijuana have been used worldwide for medical, recreational and spiritual purposes for thousands of years [80], and in the particular case of cannabis, because of the anxiolytic effects derived from its consumption [81]. A higher proportion of users of marijuana and/or other psychostimulant substances (with or without alcohol) reported “using to relax”. Although people tend to have multiple reasons for using substances, these results would be in line with those found in various studies on the motivational aspects of marijuana use, in which among the main reasons for use are to relax, wanting to feel better and to forget problems [82]. This is alarming given that Patrick et al. [82] found that motives related to Get High + Relax Reasons are considered potential reasons to continue consumption after the substance has been tried. Meanwhile, alcohol is a legally permitted substance that is widely consumed throughout the world, in both social and cultural settings [83]. This widespread use and its extensive use in social settings would justify the responses in this study that relate substance use to social integration. In a study published by Skobic et al. [84], the authors conducted a telephone interview with a sample size similar to this study of 1639 participants, and they found a high prevalence of marijuana use for sleep induction/relaxation. Substance use and its use to relax or “feel better” may also be related to the presence of associated comorbidity, such as major depressive disorder (MDD). This disorder can profoundly alter the patient’s social, family and work performance, and is the most prevalent comorbid mental disorder among people with substance use disorders [85]. Studies such as that of López and Becoña [86] evidence a correlation between cocaine use and depressive symptomatology. The results of our study found a trend towards a significant association between the score obtained in the Goldberg anxiety-depression questionnaire and substance consumption (p = 0.051). The results of our study for the consumption of psychostimulants for relaxation purposes may have been influenced by the existence of comorbidity related to anxiety, since the score on the anxiety subscale was higher in people who consume this type of substance. One third of the participants in our study say that they have at some point forgotten what they did when they drank alcohol, or took drugs or other psychoactive substances. This is the most frequently reported personal and social consequence of drug consumption, although it is strongly modulated by age [61].

Alcohol intoxication produces effects that can impair judgment and decision making, and increase participation in risky behaviors including drunk driving [87,88,89]. The study by Motschman et al. [87] reported that individuals who are under the influence of alcohol may perceive themselves as “unsafe” to drive, but “safe enough” to drive short distances, especially when their blood alcohol concentration is decreasing. Driving under the influence of alcohol or other substances is one of the most frequent consequences of alcohol use in our sample, with approximately 30% of the participants reporting having driven under the influence of at least one substance. In our study, this behavior is not related to gender, while other studies indicate that these risk behaviors are more frequent among males than females [90,91]. The frequency of this behavior decreases with age, although these risky driving behaviors are related to the perception of low risk and impulsiveness of youth [92]. The type of consumption influences the consequences of consumption; alcohol with another substance (marijuana or another psychostimulant) can therefore triple the risk. Sewell et al. [93] note that the combination of alcohol and cannabis results in greater impairment even at doses that would be negligible if they were of either drug alone.

Regarding the differences in personal and social consequences according to age, the results of our study show that forgetfulness is more frequent among young people. This could be due to a pattern of consumption with an increasing trend in this population group, as reflected in the 2021 Report issued by the Spanish Observatory on Drugs and Addictions [94]. According to this report, the prevalence of consumption (last year) is higher in the 15-34 age group, and in the case of alcohol, binge drinking has generally experienced an upward trend since 2007. Heavy drinking and binge drinking are more prevalent among males and are more heavily concentrated in the 15–34 age group. The alcoholic amnesia that causes forgetfulness occurs when high blood alcohol levels are reached in short periods of time, and are more related to the speed of intake than to the quantity [95].

As for the differences in personal and social consequences according to age, older people drink alone more often than younger people. In Spain, alcohol consumption in young people is most commonly associated with the “botellón” phenomenon. Among young people, there has been a shift away from a “Mediterranean” model of alcohol consumption, associated with meals, to an “Anglo-Saxon” model characterized by consuming drinks with higher alcohol content, in larger quantities and over shorter periods of time [96]. As for illicit psychostimulants, these are used more in specific subgroups or cultures according to Favrod-Coune and Broers [97]. Cannabis is the most widely used illicit drug among adolescents and young adults [98], and its effects have traditionally been considered less harmful than those associated with the abuse of alcohol and other illicit substances (e.g., cocaine and amphetamines) and injecting drugs [99]. According to data published by the Spanish Observatory on Drugs and Addictions [94], young people generally have a low perception of the risks associated with cannabis use, and in addition, after alcohol and tobacco, it is the psychoactive substance perceived as the most available by this population. These factors could influence the minimization of the adverse effects derived from the use of some substances among young people and their widespread use in social settings. Furthermore, in our study, living together as a family constitutes a protective factor for consumption, so that young people could limit their use of toxic substances to leisure time in the company of other young people. Confirming the results about the effect of age on abuse pattern, increasing age represents a protective factor. This may be due to the social roles associated with increased opportunities for exploration and experimentation among the younger population [100], as opposed to the social commitments of adulthood, such as being married, having children, and working full-time [101]. Although the family environment can act as a risk factor in the consumption of harmful substances, in our study, people who live in families, as opposed to those who share housing with people with whom they have no family ties (or friends), presented a lower risk of consumption. This could be in line with Brook et al. [102], who state that there are protective factors in the family environment such as conventionality, balance, maternal adjustment and strong attachment bonds in the family, which can mitigate the vulnerability of children to drug use when they relate to friends and peers who consume drugs.

We observed that being male increases the probability of consumption for almost all substances (except for marijuana/hashish, which was similar for both males and females). This finding, together with those systematically reported in previous studies [103,104], shows how the use of harmful substances continues to be an issue related to masculinity. This could be linked to the social mandates that men receive from birth, such as risk-taking or avoiding showing their emotions as ways of publicly affirming their masculinity [105]. Another possible explanation for this finding is the greater social rejection of illicit drug use among women [8]. In addition, the higher prevalence of impulsivity traits observed among males [106] and the fact that impulsivity is associated with a predisposition to the use and abuse of toxic substances and the pursuit of risky behaviors [107] could also partially explain a higher consumption of harmful substances among the male population. However, it is important to note that in recent years, a trend towards a homogenization of consumption patterns among both sexes, particularly among the younger population, has been observed in most studies [8,108]. In addition, we found that certain health habits such as smoking tobacco and the intake of stimulant beverages increase the likelihood of substance use. Previous research has generally shown that tobacco use alone predicts both alcohol abuse and illicit drug use [109,110]. These results could be explained by the gateway hypothesis, which holds that the use of a legal and easily accessible harmful substance, such as tobacco, increases the risk of starting to use another, probably more harmful, drug [111]. Meanwhile, a systematic review conducted by McKetin et al. [112] revealed that combining alcohol with caffeinated energy drinks increased the desire to continue consuming more alcohol. Approximately 12.4% of the participants indicated that their family, friends or people around them had recommended that they reduce their consumption at some point. The family may therefore be a potential resource for treatment and rehabilitation [113]. Tobacco use increases this outcome (OR = 3.370). Tobacco has been used as a predictor of other substance abuse, and as such some authors support simultaneous treatment to quit tobacco and other substances [114]. Some studies report that substance use is higher in people with chronic diseases. Wu et al. [115] found that the number of chronic diseases correlated significantly and positively with the severity of drug use. However, in our case, people with chronic illnesses report not using consumption to relax (OR = 0.655). The literature shows patterns of association between substance use, mainly of alcohol, and depressive symptoms [116,117]. A study conducted with adolescents revealed that approximately 5% of the sample openly admitted to using drugs due to sadness, feelings of failure, lack of energy and because they have family problems.

According to our data, stress reduces the probability of getting into trouble for substance use. Low et al. [118] found that stress or health concerns are inversely related to heavy drinking, perhaps due to a reflection that many young adolescents are aware of, and perhaps fearful of, the detrimental health effects of drinking.

Twenty percent of the sample reported consuming alone. In our research this situation increases among people living alone, users who are also smokers and with symptoms of depression. Some authors indicate the importance of ascertaining the context where it takes place in order to understand the risks [119]. A person who consumes alone tends to manifest negative affective traits and depressive symptoms to a greater extent [120]. The predictive model identified in our study has attempted to relate the social and personal consequences of substance use/abuse to some well-known sociodemographic and lifestyle variables, such as age, sex, smoking, stress level and depressive symptoms [94,100,103,104,109,110,114,116,117,118,120], while others are new, e.g., living alone or with family or a friend, the presence of chronic disease, sedentary lifestyle and perceived health status. These warrant further research in order to establish health-promotion strategies and policies for individuals who are more vulnerable or present risk factors to the adverse personal and social consequences of drug abuse. The COVID-19 pandemic began during the study, after which many people changed their lifestyles, and many started to work from home or lost their jobs. These factors may have contributed to the increase in using certain substances. The COVID-19 pandemic has led to measures of social distancing and confinement around the world to reduce the spread of the SARS-CoV-2 virus. These measures could lead to an unpleasant experience after separation from friends and family, and the limitation or prohibition of many daily activities (work, leisure, schools, sport). This situation may induce stress and lead to mental health problems, including an increase in the use of toxic substances [121,122,123]. According to a study conducted through a survey of 3632 participants from Belgium, during confinement, respondents consumed slightly more alcohol and smoked slightly more cigarettes compared to the previous period without confinement [122]. With respect to cannabis, no significant changes in consumption were observed in study performed in Belgium. In Spain, however, data from the Spanish Observatory on Drugs and Addictions (OEDA)-COVID 2020 survey [124], part of the National Plan on Drugs (DGPNSD) of the Ministry of Health and conducted by telephone interviewing 8780 people, show that the measures imposed to control the pandemic have especially reduced the consumption of cannabis (down 17%) and alcoholic beverages (down 8%), especially in young people, in whom the drop in alcohol consumption was as much as 25%. High alcohol consumption in the form of alcohol intoxication also decreased during the pandemic (prevalence of alcohol intoxication before the pandemic was estimated around 17.2% and during the pandemic 9.7%; the decrease in the 15–19 years’ age group was 25%). According to this survey, tobacco consumption decreased in Spain during the pandemic (prevalence of consumption before the pandemic 29.1% and during the pandemic 27.7%), except among women aged 25–34 years and 45–54 years, groups in which prevalence remains more or less stable. With respect to the use of hypnosedatives without prescription, an increase in use was observed during the Covid-19 pandemic (prevalence of use before the pandemic 1.9% and during the pandemic 3.1%). This increase was observed in all age groups and in both sexes, being higher in women. The OEDA-COVID (2020) survey also reveals that cocaine use, which is relatively rare, decreased during the pandemic, from 1.4% before the pandemic to 1% during the pandemic. On the other hand, with respect to persons over 64 years of age who were surveyed, the data show a decrease in the consumption of alcoholic beverages, from a prevalence of 34.2% to 31.8%. With respect to tobacco consumption, there was also a decrease in consumption during the pandemic, from a prevalence of 10.9% to 8.9%. The use of other psychoactive substances such as non-prescription hypno-sedatives, non-prescription opioid analgesics, cannabis and cocaine was not detected in this population group.