The invention relates to methods of enhancing selective serotonin reuptake inhibitor effects in mammals. In particular, the invention provides methods for treating selective serotonin reuptake inhibitor dependent conditions such as depression. More specifically, the present invention relates to a method of increasing the antidepressant activity of a selective serotonin reuptake inhibitor ("SSRI") by administering L-lysine-d-amphetamine in combination with an SSRi and to formulates containing the same. In a preferred aspect, the combination is administered in connection with a method of treating depression. One preferred SSRI is escitalopram. The preferred amphetamine prodrug is L-lysine-d-amphetamine.
