8. any psychiatric or neurologic illness (e.g. drug abuse, Parkinson disease, Tourette syndrome, stroke) that could affect the interpretation of the data, compliance or completion of the study will be excluded. Specific psychiatric exclusions are lifetime psychosis, current mania, substance dependence, major depression, social phobia, tic disorders, eating disorders and panic disorder. Dysthymia will not be excluded, but levels of depression will be measured with the BDI for future exploratory analysis.