Woman being comforted by therapist after learning about the average age of mental illness

Age and Mental Illness: The Average Onset of Common Mental Illnesses

While mental illness varies considerably, these illnesses can become evident at any age. And several studies contend that some of these illnesses begin in adolescence, or at about age 14. But the nature of the mental illness also plays a role – and the onset of illness can vary depending on one’s specific condition.

Here, we’ll explore a few common mental illnesses and their average age of onset.

Bipolar Disorder

Many parents are unaware, but the onset of bipolar disorder can become evident in childhood – though these cases are rare. However, the most common age when bipolar disorder becomes evident is between the ages of 17 and 18.

In addition, the median age of onset may occur by age 26. And later onset can occur as late as age 41. However, bipolar disorder does not discriminate against age as this can occur even in elderly patients.


Like bipolar disorder, severe depression can occur at any age. However, this is less evident in children under age 17. In fact, early onset of depression is age 17 while the median and late onset ages are 26 and 34 respectively.

Depression is usually diagnosed after symptoms such as overwhelming feelings of emptiness or worthlessness have been persistent for a significant amount of time. On average, most cases of depression are diagnosed between ages 21 and 46.


Requiring constant care, those who are diagnosed with schizophrenia are usually in their mid-to-late 20s. Though more commonly, this disorder is diagnosed in individuals in their mid-to-late 30s. However, though rare, some cases have been reported in children under age 13.

Additionally, most symptoms begin as strange thoughts that cannot be controlled – often including hallucinations.

Anxiety Disorders

Anxiety disorders can take many forms. And a few anxiety disorder types have been detected as early as age 15 such as separation anxiety, social phobia, and other specific phobias.

While adolescent anxiety disorder does exist and is on the rise, the average age of onset occurs between 21 and 35 years of age.

Georgetown Behavioral hospital is located in Southern Ohio and serves to provide care for persons seeking help with mental health disorders and applies a holistic approach toward therapy and restorative wellness.

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