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Substances classified as intoxicants may have both positive effects (medical or social effects) and harmful effects. The harm caused by an intoxicant may be the result of the substance itself or the way it is used. Practically all intoxicants can be harmful, physically or mentally. Substance use can result in substance abuse problems.

Substance abuse problems are mental health issues caused by intoxicants and have underlying psychological, social and biological factors. Their common denominator is that they cannot develop without exposure to an intoxicant. Practically all intoxicants can cause virtually any kind of substance abuse problems. However, the potential of an intoxicant to cause substance abuse problems varies greatly.

Harmful use

If substance use is prolonged or regular and causes health issues (such as hepatitis or injury due to an accident), we may be talking about harmful use that doesn’t involve loss of substance use control. That’s why you can usually recover from harmful use, as long as you decide to reduce or stop using the substance.


We’re talking about dependency when at least three of the following six criteria are met: 1. Craving for the substance, 2. Loss of substance use control, 3. Development of tolerance to the substance, 4. Occurrence of withdrawal symptoms when use of the substance is discontinued, 5. Continuation of substance use despite the clear harm being caused, 6. Life is revolving around substance use.

Those who are dependent can usually no longer control their substance use and are no longer able to give up. Giving up requires withdrawal (with or without treatment) and conscious long-term abstinence from using the intoxicant despite the craving. Getting rid of dependency requires adopting new behavioural, thought and reaction patterns. It is important to find new sources of pleasure and to learn ways to deal with difficult emotions without intoxicants. Those recovering from dependency should at first avoid situations, places and persons who remind them of substances and substance use. A disease classification by the American Psychiatric Association refers to harmful use and dependency jointly as substance use disorder that can be mild, moderate or severe.

Withdrawal syndrome

Withdrawal syndrome follows prolonged substance use: the person has withdrawal symptoms (both mental and physical) that impair their ability to function. Withdrawal symptoms practically always involve symptoms that are due to hyperactivity of the nervous system, such as heart palpitations, sweating and tremor, as well as anxiety and insomnia.

The clinical picture and severity of withdrawal syndrome depends on the substance used: some substances (such as alcohol and sedatives) can involve life-threatening withdrawal symptoms, whereas others (such as opioids, cannabis and stimulants) can involve symptoms that are uncomfortable but not life-threatening. At worst, withdrawal syndrome can involve a confusional state, i.e. delirium, a typical example being delirium tremens. In this condition, withdrawal symptoms are severe and the person is not oriented with respect to time, place or him/herself, and has vivid hallucinations. Delirium tends to develop after a drinking binge that stops rapidly and abruptly. If not treated, delirium can lead to death.

Substance-induced psychosis

Substances may trigger a psychosis or psychotic symptoms involving different types of hallucinations and delusions. Psychoses of this kind are called substance-induced psychoses.

The development of psychosis or psychotic symptoms is particularly common with the use of hallucinogens and stimulants. These psychoses usually involve vivid hallucinations and paranoia. The use of cannabis may also cause psychotic symptoms, although it more often triggers or advances a psychotic condition in those predisposed to psychoses due to hereditary factors. Heavy use of cannabis, particularly in early youth, significantly increases the risk of psychoses. Heavy long-term use of alcohol may result in the development of alcohol hallucinosis. A person with alcohol hallucinosis typically keeps hearing music or talking, as if listening to the radio. The problem is that in alcohol hallucinosis the music is not necessarily to your liking and cannot be switched off as a radio can. Substance-induced psychoses tend to subside rapidly, at the latest within a month following elimination of the substance from the body.

Other disorders

Heavy long-term use of substances may also cause cognitive disorders that may be reversible or irreversible. Heavy long-term use of alcohol, in particular, can cause irreversible memory deficit (amnesia) characterized by the inability to create new memories. Other substances too may cause varied cognitive disorders. Most of them subside after substance use discontinuation, but chronic impairment of cognitive functions is also possible.

Pathological intoxication is also considered a type of substance abuse problem. In this condition, intoxication is disproportionate in relation to the substance or amount used.