As if psoriasis isn’t bad enough: One in five people with psoriasis go on to develop joint problems known as psoriatic arthritis. Now researchers are figuring out that the root of psoriatic arthritis may be more than skin deep—in fact, it may reside within the gut. People with psoriatic arthritis have lower levels and less diversity of certain intestinal bacteria compared to people without the disease, reports a recent study in the journal Arthritis & Rheumatology. What does your gut have to do with your immunity, skin, and your joints? A lot, it seems. The majority of immune cells reside in your gut, and they’re influenced by naturally occurring bacteria within your digestive system. If there’s an imbalance in your gut flora—due to diet, an overuse of antibiotics, or other causes—the result can be an overactive immune system that attacks the body’s healthy tissues, leading to autoimmune conditions such as rheumatoid arthritis, multiple sclerosis, psoriatic arthritis, and more. In the study, New York University researchers found that psoriatic arthritis sufferers had lower levels of specific types of bacterium including Akkermansia, Ruminococcus, and Pseudobutyrivibrio. Normally, these bugs help keep your immune system under control, but when levels dip too low, all bets are off. Although more research is needed, study authors suggest that it may possible to treat conditions such as psoriatic arthritis with strategies that target intestinal bacteria. Probiotics, for instance, may help restore balance by increasing populations of beneficial bacteria. It may be years before scientists are able to offer a natural or diet-based solution to treating psoriatic arthritis. However, they’re getting closer to understanding how our gut flora work and what we can do to support colonies of good bacteria while staving off the bad—especially when it comes to managing autoimmune diseases like psoriatic arthritis. MORE: 26 Best Foods For A Healthier, Happier Gut