Attention deficit hyperactivity disorder (ADHD), a neurodevelopmental disorder characterised by a persistent pattern of inattention and/or hyperactivity-impulsivity, is estimated to affect 84.7 million people worldwide.
It is the most commonly diagnosed mental disorder in Australian children, and of those about 15 per cent continue to live with ADHD as adults.
Experts are continuing to investigate different substances that may be capable of providing new treatment opportunities for people diagnosed with ADHD.
Now, a recent systematic review of pre-clinical studies in animal models suggests that including caffeine in the therapeutic approach could be used to alleviate some of its symptoms.
"The therapeutic arsenal for alleviating ADHD is limited, and there is a certain degree of controversy around the use of some types of medications and stimulants, especially during childhood and adolescence," explains Javier Vzquez, one of the lead authors from the Faculty of Health Sciences at the Open University of Catalonia (UOC), Spain.
"That's why it's useful to study the efficacy of other substances, such as caffeine."
The review included 13 studies in animal models, published between 2005 and 2020, to assess the association between caffeine and ADHD-dependent variables including attention, locomotor activity, impulsive behaviour, learning, and memory.
The researchers found that regular caffeine consumption was linked to increased attention span, improved concentration, learning benefits, and improvements in some types of memory.
They also found that controlled treatment with caffeine doesn't lead to side-effects such as altered blood pressure, or an increase or reduction in body weight.
However, the results for its effects on other characteristic symptoms of ADHD, such as hyperactivity and impulsivity, are not clear.
"In diagnoses in which the problem is purely attentional, caffeine may be an appropriate therapy, but if there's a symptomatologic presence of hyperactivity or impulsivity, we must be more cautious," emphasises Vzquez.
"Our results reinforce the hypothesis that the cognitive effects of caffeine found in animal models can be translated and applied in the treatment of ADHD in people, especially at young ages such as adolescence," the authors conclude.
In Australia, it's estimated that around 4 per cent of adults (between 18 and 44 years of age) live with ADHD. The 2019 SCINEMA International Science Film Festival documentary ADHD - Not Just for Kids follows the personal journeys of adults diagnosed with ADHD late in life, challenging some of the most persistent myths surrounding the disorder.
Through interviews with leading experts, the film explores recent research in the field and explains what's happening in the brains of these individuals, and why stimulants like methylphenidate - or potentially caffeine - are used to treat their symptoms.
The film also touches on the potential link between prenatal nicotine exposure through smoking and ADHD in offspring.
However, a recent review suggests that although smoking during pregnancy is associated with ADHD offspring, it's unlikely to be the cause of it.
It has been unclear whether smoking directly causes ADHD or if this association is due to other confounding factors such as socioeconomic position, education, income, and maternal age.
The systematic review and meta-analysis looked at 46 studies that assessed the association between maternal prenatal smoking and offspring diagnosis with the disorder, and found no clear evidence to support a causal relationship. Instead, shared genetics plays a substantial role in the association.
- This article is published in partnership with Cosmos Magazine. Cosmos is produced by The Royal Institution of Australia to inspire curiosity in 'The Science of Everything' and make the world of science accessible to everyone.
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