 There are a number of non-stimulant medications, such as atomoxetine, bupropion, guanfacine, and clonidine that may be used as alternatives, or added to stimulant therapy. There are no good studies comparing the various medications; however, they appear more or less equal with respect to side effects. Stimulants appear to improve academic performance while atomoxetine does not. There is little evidence on their effects on social behaviors. Medications are not recommended for preschool children, as the long-term effects in this age group are not known. The long-term effects of stimulants generally are unclear with one study finding benefit, another finding no benefit and a third finding evidence of harm. Magnetic resonance imaging studies suggest that long-term treatment with amphetamine or methylphenidate decreases abnormalities in brain structure and function found in subjects with ADHD. Atomoxetine, due to its lack of addiction liability, may be preferred in those who are at risk of recreational or compulsive stimulant use. Guidelines on when to use medications vary by country, with the United Kingdom's National Institute for Health and Care Excellence recommending use only in severe cases, Switzerland strongly limits the authorised medications, while most United States guidelines recommend medications in most age groups.
