They think it's just normal adolescent behavior, whereas it's something more significant. Young people who experience self-injurious or suicidal thoughts are more vulnerable to acting on those thoughts because they don't fully comprehend the consequences of their actions. And depressed adolescents may abuse drugs or alcohol in an attempt at feeling better. Adolescents also may start engaging in anti-social or delinquent behavior. They're depressed, angry, unhappy about things, and they act out.
Treatment often includes both individual and family psychotherapy.
Individual counseling and therapy helps kids understand what they are feeling bad about. Always walking around with doom and gloom feeds on itself and it's self-defeating. Therapy trains them not to think depressing thoughts and scenarios. Families also need help understanding what's going on. They need support and they need guidance about how to interact with their children.