While plenty of people use cannabis a substitute for prescription drugs, others have found success using both in tandem to treat conditions ranging from chronic pain to insomnia.

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But combining weed and pharmaceuticals—safely—isn't always easy. Studies show that certain drug interactions can be beneficial, while others can be harmful. Here's what we know about how cannabis interacts with four common prescription drugs.

1. Opioids (Vicodin).

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The opioid epidemic has led many to reevaluate painkillers, the use of which can quickly lead to physical dependency. So it makes sense that people in states where marijuana is legal would be interested in using weed in lieu of prescription opioids for pain management.

Dr. Dustin Sulak, who specializes in marijuana, told ATTN: that painkillers can be effective as a short-term treatment option for serious pain, but he also pointed to research indicating that marijuana can boost the pain relieving effects of opioids—without exacerbating dangerous side effects of painkillers, such as depressed breathing.

2. Sleeping pills (Ambien).

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One of the most commonly reported effects of cannabis use is sleepiness, which has proven helpful for people suffering from sleep disorders such as insomnia. That said, for people who are taking prescription sleep aids like Ambien, the database Drugs.com cautions that marijuana can cause increased drowsiness and confusion in conjunction with prescription sedatives.

3. Anti-anxiety medication (Xanax).

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Not everyone who experiences anxiety finds relief with cannabis. In fact, some find the substance causes acute anxiety and paranoia. There's not a lot of research looking at how anti-anxiety medications interact with cannabis, but the Mayo Clinic notes that marijuana "may increase the amount of drowsiness" a person experiences from drugs like Xanax.

4. Blood thinners (warfarin).

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If you take blood-thinning drugs such as Coumadin, there's some evidence that marijuana could increase the drug's effects, which may be dangerous. A 2009 study published in The Annals of Pharmacology determined that such a drug interaction is "probable," stating that marijuana appears to inhibit the metabolization of blood-thinning medication. It's possible that such an interaction could lead to bleeding complications, though the study emphasized that further research was needed to confirm the interaction.