This psychological disorder affects people causing sadness, worthlessness, insomnia, difficulty concentrating and so on. Of the millions of people affected by depression, only a third end up seeking treatment. For those who do not seek help, depression can worsen and be affected for a longer period of time. There are multiple forms of this disorder such as major depression, dysthmic disorder, psychotic depression, postpartum depression, seasonal affective disorder, and bipolar disorder (a manic-depressive disorder).