Seasonal variation in suicidal behavior with prescription opioid medication

Suicide attempts by self-poisoning utilizing prescription opioids account for more than half of prescription drug abuse and misuse emergency calls received by poison centers. Additionally seasonal suicidal behavior using other means is a commonly replicated finding. We hypothesized seasonal behavior would exist in individuals using opioid medication as a suicide means, and that this pattern would change at different latitudes in the United States.

We used a harmonic regression strategy to investigate sinusoidal seasonal variations of suicidal behavior utilizing prescription opioids, and to contrast changes in seasonal behavior by latitude within the United States. Further, we investigated associations between suicide frequency utilizing opioid medication and frequency of dispensed opioid prescriptions.

Seasonal patterns were identified; overall, all harmonic terms were significant (p<0.05). Interaction terms of harmonic by latitude and harmonic by gender also were significant (p<0.05). After stratification, females had significant harmonic terms at all latitudes. A changing peak time period with latitude also was observed, such that the peak appeared later at more southern latitudes. Additionally, increased dispensed prescriptions rates per population were associated with increased suicidal behavior utilizing prescription opioids.

This study has limitations due to its ecological nature and to missing data that may inform our understanding of suicide risk factors, such as marital status and socio-economic status.

Suicidal behavior with prescription opioids follows a seasonal pattern that changes with latitude within the United States. Further, increased accessibility may contribute to increased suicidal attempt rates utilizing prescription opioids.