Depression is defined as a state of persistently low mood, with diminished self-esteem, loss of interest and pleasure in normally enjoyable activities, and often a feeling of helplessness and hopelessness. Nearly 6.7% of Americans suffer from depression, with higher rates in women at all ages. Rates of depression are higher in middle-age and younger old-age women, exceeding 10% of the population at those ages. Dysthymia, a chronic form of depression less severe than major depressive disorder, but lasting for two or more years, is also prevalent in the US population at a rate of about 1.5%.

Anxiety is defined as having intense, excessive, and persistent worry and fear about everyday situations that may involve panic attacks in which sudden feelings of intense anxiety, fear, or terror peak within few minutes, and can frequently incapacitate the sufferer. Anxiety disorders are the most common psychiatric disorders among adults, affecting more than 18% of the US population in any year, and nearly 29% of all people at some point in their lives.