A study from researchers at the Dartmouth Institute for Health Policy and Clinical Practice examined how medical marketing spending has changed in the past 20 years.

The research, published in JAMA last week, delved into aspects of medical marketing from DTC ads to physician marketing to unbranded campaigns. Scroll down for seven of its key findings.

DTC ads showed the most growth

DTC advertising overall hit the $9.6 billion mark in 2016, accounting for 32% of all medical marketing spending. Prescription drug DTC advertising increased by $1.3 billion in 1997 to $6 billion in 2016. The sheer number of ads also skyrocketed from 79,000 to 4.6 million, a 5,722% increase.

Most of the spending was on marketing to doctors

HCP marketing didn’t see quite as large of an increase, but in 2016 it accounted for $20.3 billion of medical marketing spending. In 1997, that figure was $15.6 billion. Most of the $20 billion came from free samples ($13.5 billion). Prescriber detailing made up $5.6 billion, direct payments to doctors for things like speaking engagements or meals was $979 million, and disease education spend was $59 million.

Three therapeutic areas saw declines in ad spend

Allergy, cholesterol, and osteoporosis drugs were the only categories that saw a decline in DTC advertising. The study’s authors attributed this to the loss of patent protection for big brand name drugs in these categories and to allergy medicines moving over-the-counter. Meanwhile, diabetes, dermatology, pain, central nervous system, arthritis, cardiac, and cancer drugs saw the biggest increases in ad spend.

Spending on disease awareness campaigns increased 10 times

DTC disease-awareness campaigns jumped from 44 in 1997 to 401 in 2016. Spending in this area more than doubled from $177 million to $430 million. The leading issues were campaigns focused on public health concerns, symptom diagnosis, mental health disorders, and conditions not conventionally considered medical problems, like low testosterone or dry eye disease.

Advertising spending increased more slowly than overall drug spending

Between 1997 and 2016, medical marketing for prescription drug increased by 60%, while total U.S. drug spending increased from $116.5 billion to $328.6 billion, a 180% increase. The proportion of marketing to overall drug spending also dropped, from 14.7% to 8.2%.

Ads from hospitals and health systems dominated health services marketing

The largest share of hospital marketing was for cancer centers, which increased from $18 million to $200 million. This is followed by mental health and addiction services ($2 million to $162 million), cosmetic surgery ($6 million to $93 million), and back and neck pain ($3 million to $89 million).

The federal drug marketing watchdog is issuing fewer warnings

Submissions asking for approval to run promotions to the Office of Prescription Drug Promotion in the FDA rose from 34,182 to 97,252 in 2016. Despite the increase in medical marketing, warning letters issued for prescription drug advertising between 1997 and 2016 decreased from 156 to 11.