Methamphetamine (METH) is a powerful central nervous system stimulant which elevates mood, alertness, energy levels and concentration in the short-term. However, chronic use and/or at higher doses METH use often results in psychosis, depression, delusions and violent behavior. METH was formerly used to treat conditions such as obesity and attention deficit hyperactivity disorder, but now is primarily used recreationally. Its addictive nature has led to METH abuse becoming a global problem. At a cellular level, METH exerts a myriad of effects on the central and peripheral nervous systems, immune system and the gastrointestinal system. Here we present how these effects might be linked and their potential contribution to the pathogenesis of neuropsychiatric disorders. In the long term, this pathway could be targeted therapeutically to protect people from the ill effects of METH use. This model of METH use may also provide insight into how gut, nervous and immune systems might break down in other conditions that may also benefit from therapeutic intervention.