Depression
Major Depressive Disorder is the most common mood disorder in the US:
The "common cold" of behavioral science.
20% of women and 5% of men will experience a major depressive episode in their lifetime.
Symptoms:
Depressed mood
Lack of organization
Lack of motivation
Sleep disturbances (early morning insomnia)
Lack of sex drive
Sense of hopelessness
Gain/loss in weight (more than 5% in 6 months)
Decrease/increase in appetite