Get professional help. If you fear that you are a danger to yourself or others, head for the nearest emergency room. Otherwise, visit your college counseling center. Ideally, the staff should be able to screen for mental illness, prescribe medication and offer short-term treatment--or refer you to someone who can. But if your college's center falls short, look elsewhere. Keep in mind that for hospitalization or skillful long-term treatment, you'll probably need to go off campus anyway.
Confide in people. Forget about the stigma. A few people need to know what you're going through so they can help. For example, a recent college graduate with bipolar disorder got extensions on papers and exams through her academic dean. She also counted on close friends to check up on her when she missed a class or failed to answer her phone.
Stick to a schedule. After learning the hard way that all-nighters and Prozac are not a good combination, an Ivy Leaguer who suffers from major depression reports that he always feels better when he exercises regularly, eats right and gets enough rest.
Get good info. NAMI.org, the website of the National Alliance for the Mentally Ill, is one of several good online resources. But beware of mental-health chat rooms, which can be long on sympathy and short on facts.
Stay away from alcohol and all drugs, legal or illegal, especially if you're taking medication for your illness, and consult your doctor before using even the mildest cold remedy.
Consider taking time off. True, you may have to forfeit some portion of your tuition and fees, but the short-term financial loss may be worth the long-term health gains. Talk it over with your parents, your doctor and your academic adviser.