This study represents one of the very few, if not the first, attempts to describe the seasonal patterns of major psychiatric illnesses, including depression, manic episodes, anxiety, OCD, headaches, and substance-related disorders in a region having an arid and dry climate with scorching summers and cold winters. Despite being a retrospective chart review, it is quite reliable due to the substantial dataset, meticulous record-keeping, and the fact that the diagnoses were made in accordance with the ICD-10.

In case of depression, the study reported the maximum OPD attendance in July and the lowest in January. Notably, the data showed a clear seasonal pattern, with the highest number of depressive cases occurring during the summer months of May, June, and July when both the average temperature and daylight hours reached their maximum. Conversely, during the winter months of November, December, and January, patient numbers dropped to their lowest levels. It is worth highlighting that depression demonstrated a positive correlation with both temperature and photoperiod. The results contradicted prior research documenting elevated rates of depression during winter months. A systematic literature review encompassing 2121 studies revealed a higher prevalence of depression during winter periods characterized by reduced daylight.[17] Many such investigations[791018] were conducted in Nordic regions or areas situated at higher latitudes, characterized by harsh winter conditions typified by extreme cold temperatures and shortened daylight hours. Rosen et al.[5] observed significantly higher rates of winter seasonal affective disorder (SAD) and subsyndromal SAD at more northern latitudes, with no discernible correlation between latitude and summer SAD. Conversely, a large-scale population study in the United States failed to identify any association between duration of sun exposure and depression prevalence.[19] Avasthi et al.’s[20] study in North India revealed a pronounced peak in depressive episodes of SAD during the summer months, particularly in May, June, and April, followed by occurrences in winter and monsoon seasons. Nonseasonal depression exhibited prevalence peaks in December and January.

We postulate that the increased incidence of depression during summer in northwest India may be attributed to elevated ambient temperatures, heatwaves, and high humidity. A systematic review and meta-analysis by Liu et al.[21] documented a positive correlation between heightened ambient temperatures and/or heatwaves and adverse mental health outcomes, including depression.

When examining cases of mania in the OPD, a distinct seasonal pattern emerged. The study observed a significant peak in mania cases during the months of June, July, and August. This peak coincided with the onset of the monsoon season, characterized by hot and humid weather, as well as the period of maximum average monthly temperature and daylight hours. Intriguingly, mania displayed a strong and positive correlation with day length.

These findings suggest that seasonal variations in temperature and daylight hours may play a significant role in the occurrence and exacerbation of mood disorders like depression and mania. Further research is needed to delve deeper into the mechanisms underlying these patterns and to explore potential implications for treatment and management strategies.

In the context of bipolar mania, a Dutch revealed an intriguing peak of depressive episodes during the summer months.[22] Symonds and Williams noted a distinct surge in manic episodes occurring primarily in August.[23] Furthermore, a comprehensive analysis, comprising 197 papers conducted by Wang B and Chen D, unveiled seasonal patterns in manic episodes for many individuals with bipolar disorder, with peaks occurring during the spring or summer.[24] In a systematic review of 51 studies, Geoffroy et al.[25] concluded that manic episodes peaked in spring and summer, followed by autumn; depressive episodes peaked in early winter and were less frequent in summer. Avasthi et al.[20] identified the highest incidence of manic episodes during the monsoon season, followed by winter. Peak incidence of mood disorders was observed from May to July in a study by Singh GP et al.[26] Another Indian study by Srivastava and Sharma[27] suggested that summer depression holds significant clinical relevance. Moreover, investigations by Rosenthal et al.[28] and Wehr et al.[29] suggest a correlation between the incidence of summer depression and factors such as decreasing latitude and increasing temperature.

The findings suggest that mood disorders may be influenced by a complex interplay of factors beyond just photoperiod or light deficiency. The heat period could also serve as a triggering factor, and socioeconomic conditions associated with monsoon seasons may play a significant role in precipitating mood disorders. Economic consequences of weather events, such as heavy rains or droughts, are crucial considerations as they can lead to financial strain and stress. Additionally, the combination of hot weather, humidity, and reduced sunlight exposure can contribute to mood problems. This complex relationship between environmental factors and socioeconomic conditions highlights the need for further study to fully understand the influences on mood disorders.[30]

In case of schizophrenia, the highest patient count occurred in July, while the lowest was in January. More patients utilized OPD services in spring and summers as compared to the winter and autumn, reflecting different conditions. Interestingly, there was no significant seasonal variation observed in relation to photoperiod or temperature. The assessment of seasonality in schizophrenia is limited compared to affective disorders. In the northern hemisphere, a nationwide analysis of hospital admissions revealed peaks in hospitalizations for schizophrenia in January and June, with a trough in December.[31] In China, a study found a relationship between reduced exposure to sunlight and an increased risk of hospital admissions for schizophrenia, particularly among females and middle-aged to elderly individuals.[32] Another study in China conducted by Shiloh et al.[18] reported a significantly higher admission rate of patients with schizophrenia during the summer.

Additionally, studies by Davies et al.[33] and Owens et al.[34] indicated that schizophrenia is more likely to occur during winter in the southern hemisphere. It is suggested that extreme temperatures and inadequate exposure to sunlight may contribute to dysfunction in serotonin and dopamine systems and disrupt circadian rhythms, leading to acute psychotic episodes in schizophrenia.[832] In a critical review, Jahan S et al.[35] observed a peak of schizophrenia admission in both summer and winter but found strong positive relation between high temperature and temperature variation and hospital admission, which is similar to the present study. Nationwide registry in Austria between 2003 and 2016 found most schizophrenic patients in January and June and minimum in December.[31] In contrary, a Chinese study done by Yao Y et al.[36] in February 2023 observed a schizophrenic peak in winter and trough in spring, while an Iranian study showed positive relation between foggy, rainy days with decreased sunlight and schizophrenia.[37] Our study could not relate strongly the increased incidence of schizophrenia with any specific season.

The diagnosis of acute and transient psychotic disorders (ATPDs) saw the highest number of patients in December, with the lowest number recorded in January. However, no correlation was found between the incidence of ATPD and temperature or photoperiod.

The highest number of patients with anxiety disorders visited the OPD in March. In contrast, the lowest attendance was recorded in November, with just 12 patients. While the general trend suggests an increase in anxiety disorders during the winter months, this difference did not reach statistical significance. Interestingly, a study by Zhang et al. in 2021,[38] analyzing data from US and Sweden health registers, found that anxiety disorders were least prevalent in the summer. Similarly, a Dutch study indicated that panic disorder and generalized anxiety disorder were more common in the winter.[22] Conversely, a study by Lepine et al.[39] in 1991 reported an increased prevalence of anxiety disorders in the summer. According to an Indian study by Singh GP et al.,[26] the maximum number of patients with neurotic stress-related and somatoform disorders came in July to September.

Among the disorders included in the study, prevalence of OCD was the least common. Increased OPD visits were recorded in the month of June, and it exhibited a moderate correlation with temperature and photoperiod, but it did not reach statistical significance. The survey conducted in the Netherlands found the highest occurrence of OCD in the autumn and the lowest in the summer.[22] However, no significant seasonal differences were observed in substance abuse and schizophrenia cases.

In cases of substance abuse disorder, the most commonly abused substance was alcohol, marking a reversal in the trend. The highest number of visits for alcohol dependence occurred in winters, but overall seasonality was not associated with an increase in alcohol use disorders.

Zhang et al.[38] reported a similar trend, with the highest number of patients seeking treatment for substance abuse in winter and the lowest in summer. Additionally, a study by D.G. Uitenbroek[40] from Scotland identified a peak in alcohol intake in December, which aligns with the findings of this present study. These results are consistent with the findings reported by Ventura-Cots et al.,[41] who observed an inverse correlation between mean average temperature and sunshine hours with per capita alcohol consumption in a global cohort.

The second most common disorder among substance abuse-related disorders was opioid dependence. The number of patients receiving treatment for opioid dependence remained relatively constant throughout all seasons. On the other hand, the incidence of cannabis-induced psychosis and other cannabis-related disorders was higher during the summer, showing a strong correlation with day length and temperature. Researchers like Palamar JJ et al.[42] from New York University have noted that the consistent decrease in marijuana use during the winter months could be due to various factors, such as a lower supply of cannabis during this time, colder weather encouraging people to stay indoors, or individuals quitting marijuana as part of a New Year’s resolution.

Limitations: The study has several limitations. Its retrospective design relies on pre-existing data, potentially introducing bias and limiting the ability to control for confounding variables or establish causality. As a single-center study, the findings may not be generalizable to other regions or healthcare settings. The exclusion of patients with multiple diagnoses or comorbid neurological illnesses could introduce selection bias, narrowing the scope of the results. Other unmeasured variables, such as socioeconomic status, cultural practices, and healthcare access, may also confound the observed patterns. Finally, the use of average monthly temperature and photoperiod simplifies the complex environmental influences, potentially overlooking other relevant factors like humidity, precipitation, and daily weather variations.