Scientists have found that ADHD is more predictive of poor mental health outcomes in adults than other neurodevelopmental conditions, like autism.
The study, led by psychologists at the University of Bath, UK, is the first to show that adults with high levels of attention-deficit hyperactivity disorder (ADHD) symptoms are more likely to experience anxiety and depression than adults with high levels of autistic traits, it said.
Until now, there has been a dearth of information on the effects of ADHD on poor mental health, with far more research focusing on the impact of autism on depression, anxiety and quality of life. As a result, people with ADHD have often struggled to access the clinical care they need to cope with their symptoms, the study said.
The authors of the study hope their findings, published in the journal Scientific Reports, will trigger new research into ADHD and ultimately improve the mental health outcomes for people with the condition, the study said.
ADHD is a neurodevelopmental condition characterised by inattention and/or hyperactivity and impulsivity. The condition is estimated to affect between 3 per cent and 9 per cent of the population.
"Scientists have long known that autism is linked to anxiety and depression, but ADHD has been somewhat neglected," said lead researcher Luca Hargitai.
"Researchers have also struggled to statistically separate the importance of ADHD and autism for mental health outcomes because of how frequently they occur together," said Hargitai.
"Our aim was to precisely measure how strongly ADHD personality traits were linked to poor mental health while statistically accounting for autistic traits," said Hargitai.
"The condition affects many people - both children and adults - and the fact that more people are willing to talk about it is to be welcomed," said Hargitai.
"The hope is that with greater awareness will come more research in this area and better resources to support individuals in better managing their mental health," said Hargitai.
The study used a large, nationally representative sample of adults from the UK population.
All participants completed gold standard questionnaires, one on autistic traits, the other on ADHD traits, responding to statements such as "I frequently get strongly absorbed in one thing" and "How often do you feel overly active and compelled to do things, like you were driven by a motor?"
The researchers found that ADHD traits were highly predictive of the severity of anxiety and depression symptoms: the higher the levels of ADHD traits, the more likely a person is to experience severe mental health symptoms.
Through innovative analytical techniques, the study authors further confirmed that having more of an ADHD personality was more strongly linked to anxiety and depression than autistic traits, the study said.
These results were replicated in computerised simulations with a 100 per cent 'reproducibility rate'. This showed, with great confidence, that ADHD traits are almost certainly linked to more severe anxiety and depression symptoms in adults than autistic traits.
"Our findings suggest that research and clinical practice must shift some of the focus from autism to ADHD.
This may help to identify those most at risk of anxiety and depression so that preventative measures - such as supporting children and adults with the management of their ADHD symptoms - can be put in place earlier to have a greater impact on improving people's wellbeing," said Hargitai.
According to Dr Punit Shah, senior author of the study, another important aspect of the new study is that it advances scientific understanding of neurodevelopmental conditions.
"By addressing the shortcomings of previous research, our work provides fresh information about the complex links between neurodiversity and mental health in adults - an area that is often overlooked," said Shah.
"Further research is now needed to delve deeper into understanding exactly why ADHD is linked to poor mental health, particularly in terms of the mental processes that might drive people with ADHD traits to engage in anxious and depressive thinking," said Shah.
"At the moment, funding for ADHD research – particularly psychological research – is lacking. This is especially pronounced when you compare it to the relatively high level of funds directed at autism," said Shah.
"As the evidence becomes clear that ADHD isn't just a childhood condition but persists throughout life, we must adjust our research agendas to better understand ADHD in adulthood," said Shah.