Opiate dependence, comorbidity and seasonality of birth

In contrast with the non-opiate dependent population, persons biologically-dependent upon opioids display an excess life-time prevalence of affective and anxiety disorders. Many of these addicts state that opiates, particularly methadone, relieve or diminish the severity of their dysphoria. The purpose of this study is to explore this phenomena by analyzing how a specific population of long-term addicts (mean years of addiction 16.9, SD 3.8) differs from a non-opiate dependent population regarding seasonality of birth.

Birth months were determined for 457 opiate dependent patients, placed onto methadone maintenance for intractable opiate dependence, born between 1930-1970 (sorted by sex, race, year and place of birth), and compared to normal US birth statistics. Affective and anxiety disorders were screened for using psychometric testing, verified by structured clinical intervals.

A significant difference was noted when comparing monthly births rates for patients and normals. Grouping the monthly data into birth trimesters (Oct-Jan; Feb-May; Jun-Sep) clearly shows this difference: opioid dependent persons--38.5/29.8/31.8%; normals--33.4/32.0/34.7%. As a group, intractable, opioid dependent patients demonstrate an increased life-time prevalence, relative to normals, of anxiety (27.8 vs. 13.9%), dysthymia (23.4 vs. 6.4%) and combined anxiety + dysthymia (17.9 vs. 1.5%); opioid dependent persons born between Oct-Jan demonstrated more anxiety (32.0 vs. 25.1%), dysthymia (29.3 vs. 19.5) and combined anx + dys (23.3 vs. 14.4) than those born in the other two trimesters.

Persons entering methadone maintenance for opiate dependence with comorbid anxiety, dysthymia or combined anxiety + dysthymia are more likely to have been born in the period of Oct-Jan. This may be due to a higher risk of developmental aberrations occurring in infants born during the light-limited portion of the year creating a later propensity for intractable, opiate dependence.