Study sheds light on seasonal trends in adolescent depression and antidepressant prescribing

By Neha MathurNov 6 2023Reviewed by Danielle Ellis, B.Sc.

In a recent article published in BMJ Mental Health, researchers determined seasonal patterns in primary care antidepressant prescribing and consultations for mental health issues in adolescents and young adults living in England, United Kingdom (UK).

Background

In past decades, mental health problems in young people have been surging. Consequently, the demand for mental health services has increased. In such a scenario, understanding whether an increased demand for mental health services is seasonal could help better plan the resources at the end of service providers. 

Studies examining the seasonal patterns of mental health issues in adults in countries like Canada, the Netherlands, and the United States (US) have yielded inconsistent results. Moreover, previous studies completed among adolescents focused on surveys or hospital admissions rather than on the population-based evidence of the seasonality of these issues.

Overall, studies examining the seasonal patterns of mental health issues and antidepressant prescribing in adolescents are lacking. 

About the study

In the present study, researchers retrieved anonymized primary care electronic health records (EHRs) of over 38.6 million adolescents and young adults seeking treatment from general practices (GPs) across the UK between 1 January 2006 and 31 December 2019 to examine when they were first prescribed selective serotonin reuptake inhibitor (SSRI) or sought consultation for depression or anxiety or tried to self-harm. Each SSRI, including citalopram, sertraline, or fluoxetine, was separately examined.

This open cohort comprised adolescents and young adults aged 14-28, further classified into sex-based groups (male and female) and three age-based groups: 14-18 years (adolescents), 19-23 years, and 24-28 years (young adults).

A team of experienced practicing general practitioners, mental health specialists, and epidemiologists reviewed the clinical code lists used to identify each mental health issue. 

The researchers analyzed nine regions of England based on the Office for National Statistics classification. Likewise, they measured deprivation based on the Townsend deprivation index. Furthermore, they analyzed five ethnic groups: White, Asian/Asian British, Black/Black British, Chinese, Mixed, others, and ethnicity unknown.

The researchers then described the number and proportion of individuals with a first record of any mental health outcome during the study period to calculate incidence rates per 1000 person-years, stratified by age and sex.

For each group, they calculated incidence rates per 1,000 person-years after combining the number of first events and person-years in each month. The researchers used Poisson regression to compute the incidence rate ratios (IRRs) for each month for all study subgroups.

Results

Of 5,081,263 participants analyzed in this study, 52.5% were female, 28.4% were residents of London, and 25.1% lived in the most deprived quintile of England. Among people with known ethnicity, 76% were White, followed by participants with Mixed, Asian, Black, Chinese, and Not Known, who constituted 11.2% of all the study participants. 

The total follow-up time of this study was over 17.9 million person-years. 

Within each age-based group, females had higher incidence rates for all mental health outcomes than males, with rates of self-harm being highest in females aged 14–18 years and the remaining outcomes' rates being highest in those aged 19–23 years.

Among participants aged 14–18 years, SSRI prescribing increased in March and remained stable until August, then began surging in September, peaking in November. SSRI prescribing rates were similar throughout the year among those aged 24–28. However, the highest rates of SSRI prescribing were observed during January-March and October-November in the 19–23 years age group.

The incidence rates of depression in participants aged 14–18 years declined during January-August, then surged again, peaking in November. Conversely, these rates were highest in January and decreased until December after a brief surge around August for participants aged 19–23 and 24–28 years.

All SSRIs and individual antidepressants exhibited similar patterns of use except in females aged 14–18 years, who had the highest incidence rates of fluoxetine prescribing in November and December. Citalopram was the most commonly prescribed antidepressant in those aged older than 18 years.

The incidence rates of anxiety peaked in May among 19–23 year-olds; however, these rates were highest in September to November in those aged 14–18 years.

The incidence rates of self-harm showed the highest declines in the July-August period for female participants aged 14–18 years. In all other seasons, these rates were similar throughout the year for all age- and sex-based groups. 

Nearly 50% of students seek advice from teachers who recommend they visit a GP for their mental health issues. It explains at least partially why the demand for mental health consultation increased at the start of the academic year and plummeted during the summer. Even though researchers could not ascertain a causal relationship, factors related to education, weather, and daylight hours might be affecting mental health in adolescents and young people. 

Conclusions

This study replicated previous findings that mental health issues among adolescents and young adults increase during winters and school terms; however, it accounts for new factors, such as deprivation and ethnicity. 

Consequently, first GP visits for depression continued to rise throughout autumn in adolescents, peaking in November. Likewise, the peak in anxiety rates occurred in May when exams took place in educational institutions.

Results for young adult groups aged 19–23 and 24–28 years were similar but differed from the patterns in the adolescents aged 14-18, suggesting that seasonal patterns vary between adolescents and young adults.

Overall, a combination of factors determines how different seasonal patterns of mental health issues persist throughout the year across age groups. Thus, further qualitative research could help gain insights into elements that affect the mental health of adolescents and how they could be supported when needed. 

Intervention studies might point to whether concentrating on school mental health sessions in the first term when the incidence rates of SSRI prescribing for mental health issues in both males and females aged 14–18 years are highest. Furthermore, research comparing the results of this study with countries in the southern hemisphere could help distinguish the effects of seasons.