There are several types of bipolar and related disorders. They may include mania or hypomania and depression. Symptoms can cause unpredictable changes in mood and behavior, resulting in significant distress and difficulty in life.

• Bipolar I disorder. You've had at least one manic episode that may be preceded or followed by hypomanic or major depressive episodes. In some cases, mania may trigger a break from reality (psychosis).
• Bipolar II disorder. You've had at least one major depressive episode and at least one hypomanic episode, but you've never had a manic episode.
• Cyclothymic disorder. You've had at least two years — or one year in children and teenagers — of many periods of hypomania symptoms and periods of depressive symptoms (though less severe than major depression).
• Other types. These include, for example, bipolar and related disorders induced by certain drugs or alcohol or due to a medical condition, such as Cushing's disease, multiple sclerosis or stroke.

Bipolar II disorder is not a milder form of bipolar I disorder, but a separate diagnosis. While the manic episodes of bipolar I disorder can be severe and dangerous, individuals with bipolar II disorder can be depressed for longer periods, which can cause significant impairment.

Although bipolar disorder can occur at any age, typically it's diagnosed in the teenage years or early 20s. Symptoms can vary from person to person, and symptoms may vary over time.

Major depressive episode

A major depressive episode includes symptoms that are severe enough to cause noticeable difficulty in day-to-day activities, such as work, school, social activities or relationships. An episode includes five or more of these symptoms:

• Depressed mood, such as feeling sad, empty, hopeless or tearful (in children and teens, depressed mood can appear as irritability)
• Marked loss of interest or feeling no pleasure in all — or almost all — activities
• Significant weight loss when not dieting, weight gain, or decrease or increase in appetite (in children, failure to gain weight as expected can be a sign of depression)
• Either insomnia or sleeping too much
• Either restlessness or slowed behavior
• Fatigue or loss of energy
• Feelings of worthlessness or excessive or inappropriate guilt
• Decreased ability to think or concentrate, or indecisiveness
• Thinking about, planning or attempting suicide

Other features of bipolar disorder

Signs and symptoms of bipolar I and bipolar II disorders may include other features, such as anxious distress, melancholy, psychosis or others. The timing of symptoms may include diagnostic labels such as mixed or rapid cycling. In addition, bipolar symptoms may occur during pregnancy or change with the seasons.

Symptoms in children and teens

Symptoms of bipolar disorder can be difficult to identify in children and teens. It's often hard to tell whether these are normal ups and downs, the results of stress or trauma, or signs of a mental health problem other than bipolar disorder.

Children and teens may have distinct major depressive or manic or hypomanic episodes, but the pattern can vary from that of adults with bipolar disorder. And moods can rapidly shift during episodes. Some children may have periods without mood symptoms between episodes.

The most prominent signs of bipolar disorder in children and teenagers may include severe mood swings that are different from their usual mood swings.

The exact cause of bipolar disorder is unknown, but several factors may be involved, such as:

• Biological differences. People with bipolar disorder appear to have physical changes in their brains. The significance of these changes is still uncertain but may eventually help pinpoint causes.
• Genetics. Bipolar disorder is more common in people who have a first-degree relative, such as a sibling or parent, with the condition. Researchers are trying to find genes that may be involved in causing bipolar disorder.

Factors that may increase the risk of developing bipolar disorder or act as a trigger for the first episode include:

• Having a first-degree relative, such as a parent or sibling, with bipolar disorder
• Periods of high stress, such as the death of a loved one or other traumatic event
• Drug or alcohol abuse

Left untreated, bipolar disorder can result in serious problems that affect every area of your life, such as:

• Problems related to drug and alcohol use
• Suicide or suicide attempts
• Legal or financial problems
• Damaged relationships
• Poor work or school performance

Co-occurring conditions

If you have bipolar disorder, you may also have another health condition that needs to be treated along with bipolar disorder. Some conditions can worsen bipolar disorder symptoms or make treatment less successful. Examples include:

• Anxiety disorders
• Eating disorders
• Attention-deficit/hyperactivity disorder (ADHD)
• Alcohol or drug problems
• Physical health problems, such as heart disease, thyroid problems, headaches or obesity