Drugs used to treat Crohn’s disease and other autoimmune disorders are among those with the greatest number of reported side effects filed with the U.S. Food and Drug Administration (FDA), according to a USA Today Network Exclusive analysis.

The analysis found an increase of five times the number of side-effect reports to the FDA in 2015 from 2004 for all drugs, amounting to more than 1.2 million reports of side effects in 2015.

Drugs which suppress the immune system to fight inflammation can cause serious and sometimes lethal infections including tuberculosis, and have been linked with blood disorders, including lymphoma, a blood cancer.

Humira (adalimumab, manufactured by AbbVie), an FDA-approved monoclonal antibody that targets tumor necrosis factor alpha (a pro-inflammatory mediator that plays a critical role in inflammatory diseases), is one of the most widely used drugs to treat Crohn’s and other autoimmune disorders.

Humira is indicated to treat children and adults with moderate to severe Crohn’s disease to reduce signs and symptoms of the disease and maintain clinical remission.

However, according the new analysis, the use of Humira has been linked to more than 200,000 reports of adverse events, including 4,200 deaths.

But the authors of the analysis consider that the surge in side-effect reports could indicate a growing number of harmed patients or more vigilant reporting of adverse events, a goal the FDA is aiming to achieve. Experts consider that both likely play a role.

Humira can also cause hepatitis B infection in carriers of the virus, allergic reactions, nervous system problems, blood problems, certain immune reactions including a lupus-like syndrome, liver problems, and new or worsening heart failure or psoriasis. Doctors should carefully consider these when prescribing the drug to patients.

Crohn’s disease is one type of inflammatory bowel disease (IBD) that causes chronic or recurring immune response and inflammation of the gastrointestinal tract, from the mouth to the anus. Symptoms include abdominal pain, diarrhea, fever, and weight loss. Other complications may occur outside the gastrointestinal tract and include anemia, skin rashes, arthritis, inflammation of the eye, and tiredness.

According to the U.S. Centers for Disease Control and Prevention (CDC), there are an estimated 1 million to 1.3 million people who suffer from IBD. The cause of the disease remains undetermined.