We had evaluated the depressive symptoms severity of 75 former heroin addicts in methadone maintenance treatment (MMT) using the 21-item Hamilton rating scale for depression (21-HAM-D) and re-assessed 63 of them 1.6+/-0.3 years later. The second mean 21-HAM-D score was lower than the first (11.8+/-8.4 versus 17.4+/-6.2, p<0.0005). Benzodiazepine (BDZ) abuse was lower although not significantly (p=0.06) during the month preceding the second analysis (32/63, 50.8%) than the month preceding the first one (40/63, 63.5%). Psychotropic medication usage was higher at the second assessment than at the first one (50/63, 79.4% versus 27/63, 42.9%, p<0.0005). 21-HAM-D score reduced significantly over time among 13 "no psychotropic medication" patients (13.5+/-6.3 versus 6.8+/-6.8, p=0.005) and in 27 who started medication following the first assessment (19.3+/-3.8 versus 11.0+/-8.4, p<0.0005), but not in those who were already taking any medication before the first assessment (17.7+/-7.0 versus 15.0+/-8.0, p=n.s). 21-HAM-D score reduced in all BDZ groups but scores were still highest in the 32 patients who continued BDZ abuse (19.4+/-5.6 versus 15.2+/-7.7) followed by 14 who stopped it (16.8+/-6.4 versus 9.6+/-9.1) and were lowest in 17 patients who never abused BDZ (14.2+/-5.2 versus 7.2+/-6.4) (repeated measured, time and group effect, each p<0.0005). Predictors for being depressed at follow-up were pre-existing depression only. Stopping BDZ abuse and starting psychotropic treatment was associated with a reduction of depressive symptoms among MMT patients.