The cause is believed to be a combination of genetic, environmental, and psychological factors.[1] Risk factors include a family history of the condition, major life changes, certain medications, chronic health problems, and substance abuse.[1][2] About 40% of the risk appears to be related to genetics.[3] The diagnosis of major depressive disorder is based on the person's reported experiences and a mental status examination.[9] There is no laboratory test for major depression.[3] Testing, however, may be done to rule out physical conditions that can cause similar symptoms.[9] Major depression is more severe and lasts longer than sadness, which is a normal part of life.[3] The United States Preventive Services Task Force (USPSTF) recommends screening for depression among those over the age 12,[10][11] while a prior Cochrane review found that the routine use of screening questionnaires has little effect on detection or treatment.[12]