A new study should give antirheumatic drug manufacturers pause. Researchers found that 52.3% of patients with psoriasis and 45.5% of those with psoriatic arthritis are dissatisfied with their treatment.

Their displeasure has had consequences. Of the 1,900 respondents with severe psoriasis, between 9% and 30% said they were not treating their disease—depending on the year, the researchers wrote in JAMA Dermatology. Among those with mild psoriasis, the untreated registered in even greater numbers, ranging from 36% to 49% of patients, while patients with moderate psoriasis fell somewhere in between, at 23% to 45% untreated.

Non-treatment and under-treatment of patients with psoriasis and psoriatic arthritis remains a significant problem in the United States, researchers concluded. “While various treatment modalities are available for psoriasis and psoriatic arthritis, widespread treatment dissatisfaction exists,” they wrote.

As for their reasons, among patients who discontinued biologic treatments in 2008, 25% said the therapy did not work, 17% reported a negative side effect, and 5% said their insurance would not adequately cover the costs of the treatment. An older study had found about 30% of those eligible for a biologic remain untreated due to injection fears.

Among those receiving treatment, 21.5% with severe psoriasis were only treated with topical agents, compared to 29.5% with moderate psoriasis. Methotrexate was cited as the most commonly used oral agent.

It’s not so clear that all the patient discontent is influencing the prescription pad, however. Biologics Humira and Enbrel, both of which are approved for psoriasis, were the two top-selling rheumatology drugs in the US for 2012. Humira, sold by AbbVie, posted sales of $4.4 billion, up 28% vs. 2011, according to company-reported data, while Amgen’s Enbrel generated sales of $4.3 billion, up 14% year-on-year, according to IMS Health.

Nevertheless, researchers recommended “efforts in advocacy and education…to ensure that effective treatments are accessible to this patient population.”