Professor Dr Uwe Fuhr, Clinical Pharmacology at University Hospital Cologne, provides answers

All addictive substances have effects that are perceived as pleasant by consumers and activate the reward system. This causes the users to consuming them repeatedly and can lead to addiction in some cases. Caffeine is also an addictive substance – but it does not cause any harm. The effects of caffeine are manageable and typically do not lead to acutely dangerous symptoms or to permanent and relevant health or social consequences for the individual or for society. Moreover, caffeine can be consumed everywhere and does not involve drug-related crime.
However, alcohol, correctly referred to as ethyl alcohol or ethanol, and cannabis with the main active ingredient tetrahydrocannabinol, have not only the intoxication effect desired by consumers, but also significant undesirable and even dangerous effects.

The vast majority of people in Germany consume alcohol completely legally, 10 percent of them to an extent that is harmful to their health. Alcohol abuse is reported in 2 percent of these cases. The recreational use of cannabis is currently not permitted. Nevertheless, 2 percent of people in Germany have used cannabis last month, and just under 1 percent have a consumption problem. While the new ‘Cannabis Act’ with its limited legalization is aimed at decriminalization and improving the safety of consumption, there are also concerns that legalization will lead to increased consumption leading to increased addiction.

The dangers of an addictive drug do not only depend on the substance consumed, but also on the type, extent and conditions of use. At least in the case of the ‘Western world’, it currently seems obvious that alcohol is much more dangerous than cannabis. Studies from countries such as the United Kingdom and New Zealand have used scales to categorize the harmful consequences caused by drug addiction which include fatalities, health damage, functional impairment, addiction, accidents, crimes, social harm and financial harm. The scale values of alcohol are about three times higher than for cannabis.

There is no doubt that the risk of an overdose with direct or indirect fatal consequences is much higher with alcohol than with cannabis, even if this is not the main risk of consumption. In the case of alcohol, the loss of control and the changes in behaviour associated with the addictive nature of consumption and the damage to the brain often lead to severe impairment of the social environment, especially with higher consumption. Behavioural changes can also be observed in cannabis users; however, they tend to affect themselves and – in extreme cases – are associated with psychoses, which occur mainly in adolescents and young adults.

Pharmacologically, a major difference is that alcohol is toxic to cells in addition to the specific effects in the central nervous system. Alcohol and its main degradation product acetaldehyde primarily damage the brain, liver, pancreas and heart directly. Alcohol consumption also increases the risk of various cancers. Tetrahydrocannabinol can also cause irreversible damage to the central nervous system, especially with prolonged use. Compared to alcohol, however, the use of cannabis has a non-specific toxic effect at most through the inhalation of combustion products when smoking joints, which plays a subordinate role compared to the non-specific toxic effect of alcohol.

Alcohol and cannabis are therefore both dangerous addictive substances that need to be handled carefully by the individual and by society. However, if you consider all factors, alcohol is more dangerous.