Gateway drug theory

Gateway drug theory (alternatively, stepping-stone theory, escalation hypothesis, or progression hypothesis) is a comprehensive catchphrase for the medical theory that the use of a psychoactive drug can be coupled to an increased probability of the use of further drugs. Possible causes are biological alterations in the brain due to the earlier drug and similar attitudes of users across different drugs (common liability to addiction). Scientific investigation of the possible causes is considered important for health policy concerning education and law making.

The concept of gateway drug is based on observations that the sequence of first-time use of different drugs is not random but shows trends. On the basis of established techniques of longitudinal studies such trends can be described precisely in terms of statistical probability. As to the interpretation of the observed trends, it is important to note the difference between sequence and causation. Both may – but need not – be coupled, a question which is subject of further research, e.g., by physiological experiments.

From a sample of 6,624 persons who had not used other illegal drugs before their cannabis consumption the overall probability of later use of further illegal drugs was estimated to be 44.7%. Subgroup analyses showed that personal and social conditions, such as gender, age, marital status, mental disorders, family history of substance abuse, Ethnicity, Urbanicity, and educational attainment influenced the height of probability.

In a sample of 27,461 persons who showed no signs of alcohol use disorder (AUD) before their cannabis consumption a second examination three years later revealed a five times higher rate (500%) of AUD compared to a control group that had not consumed cannabis. In another sample of 2,121 persons who already had AUD at the first examination the rate of persistence of AUD three years later was 74% higher in the group of Cannabis consumers than in the group of non-consumers.

A study of drug use of 14,577 US 12th graders showed that alcohol consumption was associated with an increased probability of later use of tobacco, cannabis, and other illegal drugs.

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