Opioids could do a lot more damage than previously thought, according to a new study suggests that synthetic opioids like methadone and tramadol can make antidepressants go haywire.

Synthetic opioids don’t just impact the opioid receptors in the brain, but also the serotonin and norepinephrine transporters according to the study, which was published in the British Journal of Pharmacology. Researchers arrived at that conclusion after using isolated brain cells in test tubes and adding different opioids to determine the drugs’ effects.

Researchers found that out of all the opioids they studied, a number of synthetic opioids increased the amount of serotonin in the brain. Serotonin is one of the neurotransmitters that makes people feel good, and a number of drugs, including most antidepressants, work by increasing the amount of serotonin available in the brain.

When these transmitters are inhibited, the increased serotonin leads to an increase in feelings of well-being.

However, too much can lead to a serious condition known as serotonin syndrome, which is characterized by shakiness, tremors, sweating and nausea. If left untreated, the syndrome can become life-threatening. And the risk of developing it is elevated when opioids are combined with other drugs that act on the serotonin receptors.

The authors of the study conclude that more research needs to be done, and the risk of serotonin toxicity is low, but caution people who are taking certain synthetic opioids about the possibility of serotonin toxicity, especially if the opioids are taken in conjunction with other drugs.

In the meantime, we hope researchers also look into medical marijuana as an alternative to opioid painkillers as well as another option for treating depression. If cannabis proves effective for both conditions, we could avoid the potentially deadly interaction between antidepressants and opioids by using a safer alternative.