The use of any kind of mind altering substance can have an effect on a person’s mental health, in turn causing a number of complications. One of the more common side effects of drug use is depression. Over the last decade, the United States has seen a dramatic rise in prescription opioid use, which has led to an epidemic. New research suggests that individuals who use higher doses of narcotic painkillers are at increased risk of depression, HealthDay reports. The study followed 355 patients in Texas, who reported low back pain at an initial doctor’s visit, and at one-year and two-year follow-up visits. Researchers initially concluded that those who used higher doses of opioids to manage their pain were more likely to experience depression, according to the article. However continued research indicated that most of the risk of depression is due to the duration of narcotic painkiller use, not the dose - but, higher doses usually were accompanied by longer durations of use. “A strong potential explanation of our finding that increasing opioid dose increases risk of depression could be that the patients who increase dose were the longer-using patients,” said lead researcher Jeffrey Scherrer, an associate professor for family and community medicine at Saint Louis University. “This is logical as longer use is associated with tolerance and a need to increase opioids to achieve pain relief.” Establishing a link between painkillers and depression, as well as what dosage might put patients at higher risk, “may inform prescribing and pain management” by doctors, the article reports. “We hope to find risk factors such as opioid misuse that could be in the pathway from chronic opioid use to new onset depression,” Scherrer said in a news release. “This would expand the targets for intervention to limit the risk of depression in patients who need long-term opioid therapy.” The study’s findings were published in the journal Pain.