One in 20 students sometimes use drugs like Ritalin without a doctor’s prescription, a study on students’ mental health and substance use revealed last year. The study was conducted by the RIVM, the Municipal Health Service and the Trimbos Institute.

This is dangerous, the RIVM warns, as the drugs can have side effects. Users may suffer from insomnia and heart palpitations, and the medication can also have a negative effect on their mood or cause depression. There is even evidence to suggest a link with suicide.

The RIVM decided to conduct additional research. For one week, sewage water in Amsterdam, Utrecht and Eindhoven was tested to measure the levels of ritalinic acid, a substance found in ADHD medication.

Illegal import unlikely

The results showed that the concentrations of ritalinic acid roughly matched the amount of medication prescribed to people with ADHD. This makes it unlikely that the drugs are currently being imported illegally, according to the researchers. Instead, they suspect that people are giving away or reselling their doctor-prescribed medication.

The RIVM says that more research is needed to further substantiate this theory.