If you have picked up this book, chances are that you or someone you care about struggles with depression. In addition to feeling depressed or ''down,'' ask yourself the following questions: Do you crave sweets and other carbohydrates, or tend to gain weight? Are you exhausted or tired for no obvious reason? Do you have trouble concentrating or thinking clearly? Are your feelings easily hurt by rejection from others? If you answered ''yes'' to even one of these questions, you may be suffering from a particular type of depression that does not respond well to most antidepressant drugs. Take heart. There is hope, thanks to a major medical discovery made by longtime psychiatrist Malcolm McLeod of a connection between depression, resistance of the body to insulin, faulty glucose metabolism, and how the trace mineral chromium can dramatically lift depression. Moreover, chromium is a natural treatment that is safe, effective and free of unwanted side effects. ''One of the most important books in my life. A lifelong sufferer from depression, I followed all of Dr. McLeod's suggestions and am, for perhaps the first time in my life, feeling entirely normal.''