Causes

It's not known exactly what causes atypical depression or why some people have different features of depression. Atypical depression often starts in the teenage years, earlier than other types of depression, and can have a more long-term (chronic) course.

As with other types of depression, a combination of factors may be involved. These include:

• Brain differences. Neurotransmitters are naturally occurring brain chemicals that carry signals to other parts of your brain and body. When these chemicals are abnormal or impaired, the function of nerve receptors and nerve systems change, leading to depression.
• Inherited traits. Depression is more common in people whose blood relatives also have the condition.