• depressed or irritable mood
• temper, agitation
• loss of interest in activities, apathy
• reduced pleasure in daily activities
• inability to enjoy activities which used to be sources of pleasure
• change in appetite, usually a loss of appetite but sometimes an increase
• change in weight (unintentional weight loss or unintentional weight gain)
• persistent difficulty falling asleep or staying asleep (insomnia)
• excessive daytime sleepiness
• fatigue
• difficulty concentrating
• difficulty making decisions
• memory loss (amnesia) episodes
• preoccupation with self
• feelings of worthlessness, sadness, or self-hatred
• excessive or inappropriate feelings of guilt
• acting-out behavior (missing curfews, unusual defiance)
• thoughts about suicide or obssessive fears or worries about death
• plans to commit suicide or actual suicide attempt
• excessively irresponsible behavior pattern

If these symptoms persist for at least two weeks and cause significant distress or difficulty functioning, treatment should be sought.

• physical examination and blood tests to rule out medical causes for the symptoms (for example: hypothyroidism, pregnancy, kidney disease).
• evaluation for substance abuse -- heavy drinking, frequent marijuana smoking, and other drug use can be both causes and consequences of depression. Past practice in addiction treatment was to assume depression was only a symptom of use, not a potential cause, and it was left untreated. Research now shows that this leads to increased risk of relapse. If a substance abuse problem is found, be sure that psychiatric evaluation doesn't stop at diagnosing this, but continues to assess depression and other potential psychiatric problems.
• psychiatric evaluation to assess a history of persistent sad, empty, or irritable mood and loss of interest or pleasure in normal activities. Evaluation for other potentially co-existing psychiatric disorders (such as anxiety, mania, or schizophrenia).
• assessment of suicidal/homicidal risks.
• information from family members or school personnel is often helpful in identifying depression in teens.