Telling the difference between what expected behaviors are and what might be the signs of a mental illness isn't always easy. There's no easy test that can let someone know if there is mental illness or if actions and thoughts might be typical behaviors of a person or the result of a physical illness.
Each illness has its own set of symptoms but some common signs of a mental health condition can include the following.
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One half of all mental illness begins by age 14 and 75% begins by age 24