Differences of chronological seasonality in drug overdose

Objective To investigate the association between seasonality and intentional drug overdose (IDO), a commonly seen method of self-harm in daily emergency medicine practice. Methods Cases of IDO were retrospectively selected using the International Classification of Diseases (ICD)-10 coding system (codes T36–T50), in patients who attended the Emergency Department of MacKay Memorial Hospital between January 2018 and August 2019. Data regarding age, sex, arrival time, marital status, vital signs, comorbidities, psychiatric history, social conflicts, substance of overdose, and length of hospital stay by season, were analysed using Student’s t -test and χ 2 -test. Results Of all included cases ( n = 196), IDO occurred most frequently in spring (32.1%), particularly in male patients (28/49 male cases). First-time IDO occurred most frequently in spring (51/133 first-time cases) and most spring cases were first-time IDO (51/63 spring cases). Repeat IDO occurred most frequently in autumn (20/63 repeat cases). Female conflict with father and/or boyfriend, and personality disorder in patients who overdosed, showed seasonality with a spring peak. Hospital admission rate was highest in winter (10/45 winter cases [22.2%]). Conclusion Episodes of IDO exhibited seasonality, with a spring peak, particularly for male patients, female patients in conflict with father and/or boyfriend, and those with personality disorder. Clinicians should pay close attention to the abovementioned patient groups