PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics Endocrine therapy: See Disease Characteristics Radiotherapy: Not specified Surgery: Not specified Other: At least 1 month since prior Hypericum perforatum (St. John's Wort) No other concurrent St. John's Wort No concurrent monamine oxidase inhibitors (e.g., furazolidone, isocarboxazid, meclobremide, phenelzine, procarbazine, selegiline, and tranylcypromine) No concurrent sympathomimetic amines (e.g., amphetamine, phenylpropanolamine, and pseudoephedrine) or other stimulants such as methylphenidate No concurrent serotonin reuptake inhibitors (e.g., fluoxetine, paroxetine, sertraline, venlafaxine, nefazodone, mirtazepine, buspirone, and trazodone) or tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, doxepin, imipramine, nortriptyline, and protriptyline) No concurrent serotonergic agents (e.g., lithium, meperidine, and dextromethorphan) No concurrent active treatment for anemia (e.g., transfusions or epoetin alpha)