Betel quid chewing (BQC) is a common psychoactive habit in Taiwan and other Asian regions. Evidence regarding its association with specific psychiatric disorders remains limited. This study examined associations between BQC assessed at Taiwan Biobank enrolment and major psychiatric disorders recorded in linked health-insurance claims data.

We analysed 51,522 male participants from the Taiwan Biobank successfully linked to the National Health Insurance Research Database, including 7,973 ever-users (BQC) and 43,549 never-users of betel quid (non-BQC). Psychiatric disorders included schizophrenia, bipolar disorder, major depressive disorder (MDD), depressive disorders, obsessive-compulsive disorder (OCD), panic disorder, generalized anxiety disorder, attention-deficit/hyperactivity disorder (ADHD) and dementia. Multivariable logistic regression models were constructed with sequential adjustment for age, claims-record ascertainment period, education, urbanization, cigarette smoking and alcohol drinking. No correction for multiple testing was applied across the nine psychiatric outcomes.

Compared with non-users, BQC users were older, had lower educational attainment and had markedly higher prevalence of cigarette smoking and alcohol drinking. In crude analyses, BQC was associated with higher odds of schizophrenia, bipolar disorder, MDD, depressive disorders, and panic disorder but lower odds of OCD and ADHD. After full adjustment, BQC remained associated with depressive disorders (adjusted OR: 1.19, 95% CI: 1.09–1.31). An exploratory inverse estimate for OCD (adjusted OR: 0.62, 95% CI: 0.39–0.98) was based on only 24 exposed cases. All estimates were nominal because no correction for multiple testing was applied.

In these linked Taiwanese data, BQC was modestly associated with depressive disorders, whereas associations with most other psychiatric conditions were attenuated after adjustment for sociodemographic and lifestyle factors. As BQC was assessed at a single time point and psychiatric diagnoses could predate or follow that assessment, the findings represent associations and do not establish temporality or causality.