Declining rate of substance abuse throughout the month

PURPOSE: The timing of federal disbursements of welfare, disability, and mi litary benefits may be associated with monthly patterns of substance abuse. We assessed whether this association was reflected in the pattern of psych iatric presentations to an emergency room. SUBJECTS AND METHODS: We conducted a retrospective, case-control study of 1 2,904 patient presentations to an urban emergency department for psychiatri c reasons during a 7-year period. Cases were defined as patients (n = 2403) given a primary diagnosis of substance abuse. Controls included patients ( n = 10,501) with a primary diagnosis of another psychiatric illness. We cal culated the "boundary effect" (R = 100 times the number of presentations du ring the first week of the month divided by number of presentations during the last week of the preceding month) for each month, and averaged these va lues across months to determine overall effects. RESULTS: The boundary effect was stronger for patients with primary substan ce abuse disorders (R = 134, 95% confidence interval [CI] = 118 to 151) tha n for patients with other psychiatric disorders (R = 106, 95% CI = 100 to 1 12; P < 0.001). Weekly presentations for substance abuse declined consisten tly throughout the month (P = 0.01), and declined significantly more than t he incidence of other psychiatric presentations (P = 0.005). These effects remained, after adjusting for fluctuations in presentations around holidays and the new year. The lunar cycle did not influence the incidence of prese ntations. CONCLUSION: Our results confirm that substance-related morbidity is highest at the beginning of the month and declines thereafter, corresponding to th e availability of disposable income from monthly checks. <(c)> 2001 by Exce rpta Medica, Inc.