Summary: New research from the University of Warwick links adolescent cannabis use with a higher risk of bipolar symptoms—particularly hypomania—in young adulthood.
Source: University of Warwick
Adolescent cannabis use associated with increased hypomania and bipolar symptoms in early adulthood, new study finds
Researchers at Warwick Medical School report that cannabis use during adolescence is an independent risk factor for later hypomania—episodes marked by elevated mood, increased activity or energy, impulsive behaviour, and reduced need for sleep, commonly seen within bipolar disorder and capable of disrupting everyday life.
Led by Dr Steven Marwaha, the team analysed data from the Avon Longitudinal Study of Parents and Children (ALSPAC) and found a clear association between frequent teenage cannabis use and symptoms of hypomania in the early twenties. The strongest link was observed for young people who used cannabis at least two to three times weekly by age 17, with lower but measurable increases in risk for less frequent use.
The investigators emphasise that this was a prospective analysis: cannabis use was measured in adolescence and hypomanic symptoms were assessed several years later, reducing the risk that observed associations are explained by pre-existing bipolar symptoms. The analysis controlled for a broad set of potential confounders, including gender, early environmental adversity, alcohol and other drug use, and symptoms of depression or psychosis measured at age 18.
In numerical terms, the study examined data from 3,370 participants. Using adjusted statistical models, weekly or more frequent cannabis use at 17 years of age was associated with an increased likelihood of hypomanic symptoms at 22–23 years (odds ratio 2.21, 95% confidence interval 1.49–3.28). The relationship exhibited a dose–response pattern: any cannabis use raised risk, but more frequent use carried a substantially higher risk.
Path analysis in the study also identified cannabis use as a mediating factor in two important associations: first, between childhood sexual abuse and later hypomania; and second, between male gender and hypomania. In other words, some of the increased hypomania risk linked to childhood abuse and to being male appeared to operate through higher rates of adolescent cannabis use. Importantly, the cannabis–hypomania link was not explained by concurrent depression or psychotic symptoms, suggesting a specific pathway rather than general psychiatric distress.
Dr Marwaha commented that adolescent cannabis use is common and that its psychiatric consequences deserve careful attention. He noted that the prospective nature of the findings and the dose–response pattern are consistent with a potential causal relationship. For clinicians and public health professionals, frequent cannabis use in teenagers may therefore represent an actionable target for prevention efforts aimed at reducing the subsequent development of hypomania and possibly bipolar disorder.
Cannabis remains one of the most widely used illegal substances in many Western countries. Population studies report substantial rates of problematic use; for example, estimates have reached near 9.5% in some US samples, while a smaller proportion report dependence in recent surveys in the UK. Given the prevalence of adolescent cannabis exposure, even modest increases in later psychiatric risk could have meaningful public health implications.
Source: Matthew Grant – University of Warwick
Publisher: Organized by NeuroscienceNews.com (press summary)
Image source: Public domain image used in press materials
Original research: “Cannabis Use and Hypomania in Young People: A Prospective Analysis” by Steven Marwaha, Catherine Winsper, Paul Bebbington, and Daniel Smith; published online November 28, 2017 in Schizophrenia Bulletin. DOI: 10.1093/schbul/sbx158
Background
Cannabis use is common among adolescents and has been associated with various psychiatric outcomes. The prospective relationship between adolescent cannabis use and later bipolar symptoms—particularly hypomania—has been underexplored. This study tested whether cannabis exposure in adolescence predicts hypomania in early adulthood and examined potential pathways for this association.
Methods
The analysis used longitudinal data from the Avon Longitudinal Study of Parents and Children. Cannabis use at age 17 was related to hypomanic symptoms at age 22–23 using regression models that adjusted for gender, early environmental risks, alcohol and other drug use, and concurrent depressive and psychotic symptoms. Path analysis explored direct and indirect effects and whether gender, childhood family adversity, or childhood abuse increased hypomania risk through higher cannabis use.
Results
Among 3,370 participants, frequent cannabis use (at least two to three times per week) at age 17 was associated with subsequent hypomania (adjusted OR 2.21, 95% CI 1.49–3.28). A dose–response relationship was apparent. Cannabis use also mediated the links between childhood sexual abuse and later hypomania, and between male gender and later hypomania. The association was not explained by depression or psychotic symptoms.
Conclusions
The findings indicate that adolescent cannabis use may be an independent risk factor for future hypomania, with evidence consistent with a possible causal pathway. Cannabis use also appears to mediate some of the association between early abuse and later hypomanic symptoms, supporting the idea that reducing frequent adolescent cannabis use could be a feasible target for indicated prevention strategies aimed at lowering the risk of bipolar-spectrum symptoms.