Some of the substances that have been marketed as treatments for ADHD include pycnogenol, an antioxidant derived from pine bark; melatonin, another antioxidant known to successfully treat sleep cycle disturbances in certain children; gingko biloba extract, often used in Europe to treat circulatory and memory disorders; and such herbs as chamomile, valerian, lemon balm, kava, hops, and passion flow