It is found that the first symptoms occur two to four years prior to the onset of a diagnosable disorder. Major Depression, clinically known as Major Depressive Disorder (MDD), is the leading cause of disability in the U.S. between the ages of 15-44. Major depression affects approximately 14.8 million American adults, or about 6.7 percent of the U.S. population (age 18 and older) in a given year.

Dysthymic Disorder is mild, chronic depression that lasts for at least two years for adults and at least one year for children. Symptoms typically come and go over a period of years, and their intensity can change over time. The median age of onset is 31.Bipolar Disorder causes intermittent shifts from symptoms of depression to mania (excessive highs of euphoria and/or energy). These symptoms can shift daily, monthly, even yearly, and in some cases simultaneously. NIMH reports that 5.7 million adult Americans (2.6% of the population) suffer from bipolar disorder. The median age of onset is age 25.Schizophrenia is a chronic disorder characterized by brain disorders which cause people to interpret reality abnormally, often with hallucinations, delusions, disordered thinking, and disturbed behavior. 

Schizophrenia is a disorder that requires lifelong treatment. The onset for males is typically in the late teens or early twenties; the onset for females is typically late twenties or early thirties. NIMH estimates that 2.4 million American adults, or about 1.1% of the population, age 18 and older, in a given year suffer from the disorder. Anxiety Disorders include Panic Disorder, Obsessive-Compulsive Disorder (OCD), Post-Traumatic Stress Disorder (PTSD) [see below], Generalized Anxiety Disorder (GAD), and Phobias (social phobia, agoraphobia, and specific phobia). Over 18% of adult Americans (approximately 40 million) suffer from an anxiety disorder within a given year. Approximately 1 in every 4 children/adolescents suffers from an anxiety disorder, within a lifetime prevalence.

These disorders often occur simultaneously with other anxiety disorders, depressive disorders, or substance abuse. Three-fourths of people with anxiety disorders have an onset of their first episode by the age of 21. (Source: NIMH) Post-Traumatic Stress Disorder (PTSD) is a type of anxiety disorder which is triggered by experiencing or witnessing a traumatic past event. PTSD causes the individual to have difficulty coping to the extent that it interferes with their daily life. The disorder usually occurs after violent personal attacks (such as rape, mugging, or domestic violence), war, terrorism, natural disasters, or accidents. NIMH reports that approximately 7.7 million adults in the US (3.5%) suffer from PTSD within a given year.