The ECDD assesses the health risks and benefits of the use of psychoactive substances according to a set of fixed criteria.

For the Single Convention on Narcotic Drugs, 1961, these criteria include:

• Similarity to other substances under the Convention with regard to the dependence potential of the substance and actual abuse, and/or evidence of likelihood of abuse,
• Is likely to produce similar harm to public health as substances already controlled under the Convention
• Therapeutic applications of the substance.

For the Convention on Psychotropic Substances, 1971, these criteria include:

• Evidence that the substance has a dependence potential and capacity to produce psychoactive effects,
• Similarity to other substances under the Convention with regard to abuse and/or evidence of likelihood of abuse,
• Extent of harm to public health and social problems, or likelihood to cause these harms,
• Therapeutic applications of the substance,

Depending on the outcome of the assessment of a specific substance the Committee may advise:

• To place the substance under international control (place it in one of the Schedules)
• To transfer the substance from one Schedule to another (leading to more or less control measures)
• To delete the substance from a Schedule (putting an end to control)
• To keep the substance under surveillance out of a lack of evidence for actual abuse or dependency.

The ECDD recommendations are presented by the Director General of the WHO to the UN Secretary General and the United Nations Commission on Narcotic Drugs (CND).

The recommendations of the Expert Committee are based on the best available scientific, medical and public health evidence and must comply with the criteria established in the conventions. Specific rules and procedures for the evaluation of substances are published in Guidance on the WHO review of psychoactive substances for international control. The process of substance evaluation has evolved over time and the methods of the Expert Committee are continuously adapted to maximise the scientific rigour of the review process and to enable inclusion of emerging data sources.

The CND convenes each year in March in Vienna and reviews the global drug situation, considering the interrelated issues of prevention of harmful substance use, treatment for substance use disorders and supply and trafficking in illicit drugs. It takes action through resolutions and decisions. The CND decides, on the basis of recommendations by the WHO, whether to place narcotic drugs and psychotropic substances under international control.