There are several types of depression. While they are all characterised by intense low mood, there are also important differences. Major depression Major depression is also known as major depressive disorder. The most recognised symptom is low mood and loss of interest in activities that you once considered pleasurable. These symptoms can be mild, moderate or severe, but usually interfere with your daily life and relationships. The low mood persists for at least 2 weeks, and will be experienced on most days. Sub-types of major depression include: melancholic depression, a severe form of depression that includes physical as well as emotional symptoms psychotic depression, which includes hallucinations (hearing or seeing people or things that aren't there); delusions (false beliefs that other people don’t experience or agree with); or paranoia (feeling suspicious of other people or feeling that everyone is against them) Bipolar disorder Bipolar disorder is characterised by extreme mood changes that disrupt daily life. Symptoms of manic episodes include: extremely high energy in speech and activity agitation reduced need for sleep finding it hard to focus Symptoms of depressive episodes are similar to those of major depression. People who have bipolar disorder can also experience episodes of psychosis (hallucinations, delusions and/or paranoia). Cyclothymic disorder Cyclothymic disorder is sometimes described as a milder form of bipolar disorder. The person experiences changing moods for at least 2 years. They have periods of hypomania (a mild-to-moderate level of mania) and episodes of depressive symptoms. They may also have very short periods of even moods, with fewer than 2 months in between. Symptoms tend to be less severe and are shorter lasting than in bipolar disorder or major depression. Dysthymic disorder Dysthymic disorder is similar to major depression, but with fewer severe symptoms that persist for at least 2 years. Seasonal affective disorder Seasonal affective disorder (SAD) is a mood disorder (either depression or mania) that has a seasonal pattern. Depressive symptoms tend to start in winter and fade by spring. It can take several winters to diagnose this type of depression. SAD is thought to be triggered by changes in exposure to light in the winter and is more common in countries with short days and long periods of darkness, such as in the cold climate areas of the Northern Hemisphere. SAD is very rare in Australia. Perinatal depression Perinatal and postnatal depression occurs during pregnancy or after the birth of a baby and affects up to 1 in every 5 females in Australia. It is associated with the challenges and demands of parenthood as well as changes in hormones. For males, new routines and roles can also trigger depression. While tiredness and irritability are normal during pregnancy and after the baby is born, if you or your partner experience low mood that persists for more than 2 weeks, it’s important to talk to your GP or community health nurse about whether it may be perinatal depression. All types of depression can be treated and the earlier you seek support, the better. Speak with your doctor about which treatment might be most effective for you.