Vyvanse does not reduce the effectiveness of Citalopram. However, Vyvanse can potentially cause side effects such as agitation, insomnia, or loss of appetite that may mimic symptoms of depression. It is important to consult with a healthcare provider if you feel that your symptoms are not well controlled with Citalopram to determine if a dose adjustment may be necessary. Overall, if both medications are well tolerated and effectively managing your symptoms, there is no contraindication to continue both treatments.