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Overdiagnosis of adult attention-deficit hyperactivity disorder in British Columbia has led to a surge in stimulant medication use despite limited evidence of its long-term effectiveness, according to a new publication.

Data compiled by the University of B.C.’s Therapeutics Initiative show that throughout the 2000s, ADHD medication use remained stable among diagnosed B.C. residents aged 18 and older, at one or two users per 1,000 population. That number climbed gradually during the 2010s and then increased considerably during the COVID-19 pandemic, peaking at 16.6 per 1,000 population last year.

Both the longer-term pattern and acute spike have been seen elsewhere, including the U.S. and Australia. Researchers have attributed it to a number of reasons, including increased awareness of the neurodevelopmental condition, health system pressures, misdiagnosis and pandemic-related factors such as the impact on mental health and the expansion of telehealth diagnoses, which tend to be less comprehensive than in-person visits.

The therapeutics letter, published Tuesday, notes that a reliable ADHD diagnosis is complex, with no simple diagnostic test available. Competent diagnosis requires comprehensive family, gestational and developmental history plus observations over time, such as documented symptoms from childhood or a history of substance use. Side effects of treating ADHD with stimulants and atomoxetine can include increased blood pressure and heart rate, appetite suppression, anxiety, aggression and, in rare cases, sudden cardiac death and acute psychosis.

The letter said prescribing decisions should involve informed patient consent, including “a clear understanding of potential harms and the paucity of evidence about long-term effects. Patients should appreciate, as for other drugs affecting the brain, that stimulant dependence and withdrawal symptoms are possible.”

Evidence for pharmacotherapy of adult ADHD is derived almost exclusively from randomized controlled trials lasting 12 weeks or less. “Most systematic reviews and meta-analyses conclude that evidence for efficacy and safety from short-term treatment is weak, and limited mostly to rating scale scores,” the letter said, referring to subjective point scales used to score behaviours. “They all conclude that we know very little about long-term drug treatment.”

Long-term stimulant use can lead to tolerance and dependence, and some product monographs for ADHD medications warn about the potential requirement for increasing doses, physical and psychological dependence, and possible misuse, the letter said. It cited as an example the website of the ADHD medication Vyvanse, which states that the drug has a “high chance for abuse and may cause physical and psychological dependence.”

The UBC Therapeutics Initiative is an independent organization that provides evidence-based information to health professionals and the public about drug therapies. Therapeutics letters are published bimonthly.

Josh Levin, a Victoria-based family doctor who helped to develop and review the latest letter, says he is worried that people may be confusing environmental, cultural and social influences with ADHD symptoms.

“One thing that’s been raised by other experts is the idea of the impact of digital media on people’s perception of their own symptoms as inattention and impulsivity,” he said.

“I think we sometimes have to take a step back and realize that social media, and digital media in general, is premised on the goal of getting your attention as quickly as possible, for short periods of time. … It pulls our attention by design in lots of different directions. It’s easy to feel, as you jump from one video to the next bit on Twitter, that you’ve actually got a problem with your attention.”

Dr. Levin added that existing health system pressures have made it difficult to provide meticulous diagnoses. Most primary care doctors don’t have the time to explore a patient’s childhood and family history – assessments that are better suited for psychiatrists, for which there are months-long waits in B.C. Obtaining a thorough diagnosis is “borderline impossible,” he said. “It would take so long to do that, that I think people would either get frustrated and look elsewhere, or they would just throw their hands up and stop looking.”

Martin Gignac, chair of the Canadian ADHD Research Alliance (CADDRA) and an associate professor of psychiatry at the University of Montreal, said that while the increase in diagnoses requires exploration, he disagreed with the assessment that adult ADHD is generally “overdiagnosed.” He cited 2006 research led by Harvard Medical School health care policy professor Ronald C. Kessler that estimated 4.4 per cent of U.S. adults have ADHD, with just a fraction receiving a diagnosis for it.

(The Centre for ADHD Awareness Canada says the disorder affects 4 per cent to 6 per cent of adults and 5 per cent to 7 per cent of children. Estimates can vary depending on assessment methods.)

“When you look at the population prevalence of the disorder and the rate of prescription in many different age groups, we’re not above the population prevalence,” Dr. Gignac said. “In adults, we tend to believe that we are under the prevalence rate that we should expect. I would say, most likely, there are a number of individuals who are misdiagnosed, that get treated with those medications that maybe require something else.”

He added that while there is potential for people to abuse stimulant ADHD medications, there is no link to increased risk of substance abuse when they are taken as prescribed. Rather, studies have shown that ADHD medication can offer some protective effect against substance abuse.

There are also a number of non-pharmacological options for managing ADHD symptoms, including getting adequate sleep, exercise and mindfulness meditation. The letter notes there is limited evidence for non-drug treatments such as cognitive behavioural therapy.

CADDRA, in partnership with the Centre for ADHD Awareness Canada and the Canadian Research and Education for the Advancement of Child Health program, has issued a white paper on equitable access to ADHD care that is being presented to provincial and federal governments. It recommends training more medical and mental health practitioners in assessment diagnosis and treatment, developing educational resources for the public and training educators to support students with ADHD.

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