Methamphetamine use stimulates the brain and central nervous system, and can result in a variety of adverse outcomes. The effect that methamphetamine has on an individual depends on a number of factors. These include:

• how much methamphetamine is taken
• the method of use
• the form and purity of the methamphetamine
• the height and weight of the user
• the user’s current physical and mental health status
• the user’s previous experience with methamphetamine (i.e. new user vs frequent user)
• whether other substances (alcohol, tobacco, medications, or other illicit drugs) are used at the same time as methamphetamine.

There are a variety of mental health risks associated with methamphetamine use. Many of these risks are very serious, and can result in severe short- and long-term consequences for the user.

The effects of methamphetamine are the same regardless of which form (e.g. powder/base/crystal) is used. However, crystal methamphetamine (ice) tends to be more potent and purer than other forms, and is also more likely to be smoked or injected. As a result, the effects of ice are both more likely to occur and likely to be more intense than when other forms of methamphetamine are used.

People who regularly use methamphetamine may experience a range of negative impacts on their mental health, including:

• depression and anxiety
• agitation and mood swings
• violence and aggression
• impaired cognitive function, concentration, and lack of motivation.

There is a strong association between methamphetamine use and psychosis. Methamphetamine use can cause psychotic symptoms in otherwise healthy people, and can also trigger or exacerbate psychosis in people who have pre-existing mental health conditions.

Regular use of methamphetamine may also lead to dependence (addiction). Dependent users develop a tolerance to methamphetamine, and need to take larger doses of the drug to achieve the same effect and feel ‘normal’. The urge to use methamphetamine can become more important than other activities in their lives, resulting in poor physical and mental health, social and financial problems, and family and social breakdown. See FAQ What are the diagnostic criteria for methamphetamine-related mental health disorders?

For more information about the effects of methamphetamine, see FAQs What are the short-term effects of methamphetamine use? and What are the physical health risks of methamphetamine use?