While we all feel sad, moody or low from time to time, some people experience these feelings intensely, for long periods of time (weeks, months or even years) and sometimes without any apparent reason. Depression is more than just a low mood – it's a serious condition that affects your physical and mental health.
Occasional anxiety is a normal part of life. You might feel anxious when faced with a problem at work, before taking a test, or making an important decision. But anxiety disorders involve more than temporary worry or fear. For a person with an anxiety disorder, the anxiety does not go away and can get worse over time.
Bipolar disorder is a serious brain disorder in which a person experiences extreme variances in thinking, mood, and behavior. Bipolar disorder is also sometimes called manic-depressive illness or manic depression. People who have bipolar disorder commonly go through periods of depression or mania.