http://en.wikipedia.org/wiki/Clinical_depression
Signs and symptoms:
Depressed mood, or
Loss of interest or pleasure.
It is sufficient to have either of these symptoms in conjunction with four of a list of other symptoms. These include:
Feelings of overwhelming sadness or fear, or the seeming inability to feel emotion.
A decrease in the amount of pleasure derived from what were previously pleasurable activities.
Changing appetite and marked weight gain or weight loss.
Disturbed sleep patterns, such as insomnia, loss of REM sleep, or excessive sleep.
Changes in activity levels, such as restlessness or a slowing of movement.
Fatigue, either/both mental and physical.
Feelings of guilt, helplessness, hopelessness, anxiety, and/or fear.
A decrease in self-esteem.
Trouble concentrating or making decisions, or a generalized slowing and obtunding of cognition.
Self-harm or ruminating on self-harm.
Ruminating on death and/or suicide.
Reduced memory.
Depression in children is not as obvious as it is in adults. Here are some symptoms that children might display:
Loss of appetite.
Sleep problems, such as recurrent nightmares.
Learning or memory problems where none existed before.
Significant behavioural changes; such as withdrawal, social isolation and aggression.
An additional indicator could be the excessive use of drugs or alcohol. Depressed adolescents are at particular risk of further destructive behaviors, such as eating disorders and self-harm.
/Spader