In one aspect, the present invention is directed to methods for treating fatigue, neurobehavioral slowing and other cognitive disorders and defects due to cancers and treatments associated with cancers, and similar conditions. In a further aspect, the present invention is directed to methods for treating disorders related to menopause, including executive function defects. The methods involve the administration of a composition comprising D-threo methylphenidate that is substantially free of L-threo methylphenidate and of erythro forms of methylphenidate.