Drug and Alcohol Problems Linked to Higher Risk of Suicide, Major Study Finds

Scientists in Sweden studied more than 4 million people to learn how drug and alcohol problems connect to suicide. They found that people with substance use disorders — serious problems with alcohol or drugs — were much more likely to have suicidal thoughts or actions. The study looked at health records going back 47 years. Researchers wanted to know not just if the link existed, but also whether it ran in families.

Researchers used health records from Sweden's national databases to do their work. Every person born in Sweden gets a special ID number that links all of their medical records together. The team looked at people born between 1958 and 1999, and ended up studying about 4.2 million people. This made it one of the largest studies of its kind ever done.

The study looked at many different kinds of substance use disorders, or SUDs. These include problems with alcohol, opioids, cannabis, sedatives, and stimulants. People were placed into groups based on what kind of SUD they had — alcohol only, drugs only, or both. Having both types of problems was linked to the highest risk of suicidal behavior.

The researchers also tracked suicidal behavior, which they defined as either a suicide attempt or a death by suicide. They were careful to separate accidents from acts that were clearly intentional. This helped make sure the results were as accurate as possible. Even after accounting for other mental health conditions, the connection between SUD and suicide was still strong.

One big question the team asked was: why does this connection exist? Is it because of the substance use itself, or could something in a person's genes or family background raise the risk for both? To find out, researchers looked at relatives — including twins, brothers and sisters, half-siblings, and cousins. The closer the family relationship, the stronger the link they found.

If a person had a relative with a substance use disorder, that person was also more likely to show suicidal behavior. Full siblings showed a stronger connection than half-siblings or cousins. This pattern suggests that genetics — traits passed down through families — plays a role in both drug problems and suicide risk.

Researchers also noticed something interesting about half-siblings. Half-siblings who share a mother tend to grow up in the same home, while those who share only a father often don't. When the link was stronger among siblings raised together, it suggested that the home environment also matters, not just genes. Both nature and nurture seem to be involved.

The scientists took many other factors into account, like a person's sex, birth year, and parents' education level. Mental health conditions like depression, ADHD, and anxiety were also considered. Even after all these adjustments, the connection between substance use and suicide stayed strong. This made the researchers more confident in their findings.

The findings are important because they suggest that treating substance use disorders could help reduce suicide risk. They also point to the need to look at a person's family history when thinking about mental health. If a close relative has struggled with drugs or alcohol, it may be a warning sign worth paying attention to. Researchers hope this work leads to better prevention and support for people who are at risk.