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Ice and the brain

Ice (crystal methamphetamine)  triggers the release of two chemicals in the brain, called dopamine and noradrenaline. These chemicals are also released during pleasant activities - like eating and sex - and they are responsible for making us feel alert and excited. But flooding the brain with these chemicals can cause an 'overload' in the system which is why some people can’t sleep for days or experience symptoms of psychosis after taking ice.

Ice also stops the brain from reabsorbing these chemicals which lowers their supply in the brain. This is why people often feel low or irritable for 2-3 days after taking ice.

Over the long term, regular use of ice can damage or destroy dopamine receptors in the brain - sometimes to a point where the person using the drug no longer feels normal without having ice in their system. Even after people have stopped using ice it can take up to a year before these brain changes return to normal.

What are the effects of ice?

The initial effects of ice often last for between 4 and 12 hours depending on how much ice is consumed. Although the effects of ice are usually felt quickly (within minutes if it is smoked or injected, or about 30 minutes if snorted or swallowed), it can take 1 to 2 days to entirely leave the body. The effects of ice can be both physical and mental

The physical effects of ice can include:

  • Headaches and dizziness
  • Dilated (enlarged) pupils and blurred vision
  • Dry mouth
  • Jaw clenching, teeth grinding
  • Insomnia
  • Increased attention, alertness and talkativeness
  • Trembling
  • Sweaty, cold and clammy skin
  • Repeating simple things like itching and scratching
  • Increased breathing and body temperature
  • Increased heart rate and blood pressure
  • Reduced appetite
  • Stomach cramps, nausea and vomiting
  • Dehydration
  • Aggressive behaviour
  • Increased energy
  • Changes in sexual arousal or sexual drive (libido)
  • Stroke
  • Dental problems: increased tooth sensitivity, cracked teeth and cavities, gum disease
  • Dependence
  • Poor concentration and memory
  • Increased risk of tetanus, infection and vein damage (if injecting)
  • Increased risk of blood borne viruses e.g hepatitis B, hepatitis C, HIV/AIDS (if sharing needles)
  • Heart and lung problems, chest pains
  • Kidney problems, including kidney failure
  • Malnutrition and weight loss
  • Exhaustion
  • Movement problems

Use of methamphetamines (including ice) is also associated with elevated mortality rates relating to overdose, natural diseases (such as coronary disease), suicide and accidental injury.

It is also important to know that mixing ice with other drugs, including over-the-counter or prescribed medications, can cause enormous strain on the body. This increases the risk of negative mental and physical effects as well as increasing the likelihood of overdose. Learn more about the risks associated with “using ice with other drugs”.

The ComeDown Phase and Withdrawal

A 'comedown' phase or ‘crash’ is often experienced by people who use ice as the drug starts to wear off. These feelings can last a few days and symptoms can include:

  • Feeling down or depressed
  • Decreased appetite
  • Exhaustion
  • Increased need for sleep
  • Irritability
  • Feeling anxious.

Withdrawals refer to unpleasant symptoms experienced by people with a dependence on ice. These symptoms can last for several days or many weeks, depending on the severity of use. Withdrawal symptoms can include:

  • Headaches
  • Anxiety
  • Aggression
  • Restlessness
  • Cramps
  • Vomiting.

For more information about treatment and support options available to people who are experiencing problems with ice and other drugs please visit “what type of help is available”.  Information about what to expect from the withdrawal, treatment and recovery processes is also discussed.

How to help someone who may be experiencing an overdose

The effects of ice can be unpredictable, as there is no quality control when an illegal drug is made. It can be cut or mixed with a number of other substances increasing the risk of unpredictable side effects.

Serious side effects and symptoms of a possible overdose include:

  • Racing heartbeat and chest pain
  • Panic attacks
  • Extreme confusion or agitation
  • Overheating and dehydration
  • Exhaustion or unconsciousness
  • Fits, seizures or convulsions
  • Stroke or heart attack

Call an ambulance (000) if someone is showing any of these symptoms. For more information about how to help someone who has taken ice please visit “how to protect yourself and others”.


Australian Drug Foundation. (2016). Amphetamines. Melbourne: State Government Victoria.

Australian Institute of Health and Welfare. (2018). Alcohol, tobacco & other drugs in Australia. Canberra: Australian Institute of Health and Welfare.

Darke S., Kaye S., McKetin R., Duflou J. (2008). The major physical and psychological harms of methamphetamine use. Drug Alcohol Rev 2008; 27: 253–62.

Darke, S., Kaye, S., and Duflou, J. (2017). Rates, characteristics and circumstances of methamphetamine-related death in Australia: a national 7-year study. Addiction.

McKetin, R., & Black, E. (2014). Methamphetamine: What you need to know about speed, ice, crystal, base and meth. Sydney: National Drug and Alcohol Research Centre, University of New South Wales.

See ‘The effects of ice on the brain’ fact sheet for sources related to cognitive effects.

Page last reviewed: Friday, 9 August 2019

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