Most have other conditions as well, like attention-deficit hyperactivity disorders, sleep problems or epilepsy, which may affect their functioning, Dr. Gillberg said.

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It used to be red-flag disorders like autism and attention-deficit hyperactivity disorder that attracted attention in early childhood.

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In particular, there's a strong genetic component to attention deficit hyperactivity disorder, as well as to several mood and anxiety disorders, including depression, bipolar disorder, and obsessive-compulsive disorder.

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