The study found that both mothers' ratings and adolescents' self-ratings of depression symptoms predicted the adolescent's future depression, antisocial behavior, mental impairment, the use of health services, and regular tobacco use. The mothers' own depressive symptoms were not significantly associated with adolescent depression, the use of health services, or substance use at the 4-year followup. Depression that was accompanied by adolescent-rated suicidal thoughts was more strongly linked with mental impairment at followup than depression alone. The findings indicate it is possible to obtain clinically useful information on adolescent depression from the adolescent's mother; however, information on suicidal thoughts was rarely endorsed by mothers, which suggests that maternal reports of adolescent suicidal thoughts show less sensitivity to this symptom of depression than adolescent reports. This was a longitudinal study of 842 adolescents ages 11 to 16 at the baseline assessment and ages 15-20 at followup, with 62 percent retention at followup. The sample was obtained from the Cardiff Study of All Wales and Northwest England Twins. The data used came primarily from two waves of data collection, the first in 2000 and the second in 2004. Data on adolescent depression were collected with the adolescent and maternal report of the Mood and Feelings Questionnaire. Mothers reported on their own current mood state by completing the depression subscale of the Hospital Anxiety and Depression Scale. Antisocial behavior, functioning, health service use, and alcohol and tobacco use were measured at baseline and followup. 4 tables and 28 references