Obesity 'linked to ADHD'

A drug “used to treat hyperactive children” could help to “solve Britain's obesity crisis,” The Daily Telegraph has claimed. The newspaper says that a new study has shown one-third of severely obese adults who fail to lose weight have undiagnosed Attention Deficit Hyperactivity Disorder (ADHD).

The researchers behind this study suggest that untreated ADHD stops the severely obese “from having the willpower to lose weight”, and that ADHD drug treatment ‘dramatically’ improves their ability to lose weight.

However, this study has a number of major limitations, making it difficult to determine the true effects of ADHD treatment on weight loss or even how common ADHD actually is among those with persistent weight problems.

Also, drugs used to treat ADHD are also stimulants and known to induce weight loss, even in people without ADHD. Therefore, these drugs may be inducing weight loss not through specifically treating ADHD but by some other mechanism, such as increasing alertness and activity. These drugs can have side effects and are not licensed for use to aid weight loss.

Where did the story come from?

Dr Lance D Levy and colleagues working in a private clinical practice in Toronto carried out this research. No direct sources of funding for the study were reported but one author reported receiving an unrestricted grant from Shire Pharmaceuticals (who make one of the drugs used in the study – Adderall XR), which had funded previous presentations about the role of ADHD in weight loss failure.

The study was published in the peer-reviewed medical journal, the International Journal of Obesity.

What kind of scientific study was this?

This was a non-randomised controlled trial looking at the weight loss effects of ADHD treatment in severely obese people diagnosed with ADHD.

The researchers screened 242 adults (aged less than 66 years) for ADHD. These were individuals who had been referred to them as being severely obese and not being able to lose weight. This screening process involved identifying those likely to have ADHD through the use a number of standard questionnaires and several clinical interviews to obtain a thorough medical history.

A subset of 242 people identified in this screen were then given a two-hour structured clinical interview with a clinical psychologist and this confirmed an ADHD diagnosis in 62 people. An additional 16 people were diagnosed with ADHD based on a lifelong history of problems consistent with ADHD. This was assessed in five to eight clinic visits and supported by questionnaire scores.

In total, this gave 78 people with ADHD: 72 women and six men with an average age of 41.3 years and average body mass index of 42.7kg/m2 .

These 78 participants were also screened for other conditions that can occur with obesity, such as binge eating disorder, mood disorder, sleep apnoea, chronic pain and gastro-oesophageal reflux. Any obesity-related conditions identified had to show significant improvement with treatment before starting treatment for ADHD.

All 78 participants were then offered treatment for ADHD, which continued for an average of 466 days. Thirteen participants did not accept treatment, or did not remain on their ADHD treatment due to side effects or a lack of benefit. These 13 people were used as controls. These controls did take part in all other parts of the weight loss management process, which included a dietary intervention and activity counselling.

Participants’ ADHD symptoms and their effect on the participants’ lives were recorded during assessment, such as inattention, procrastination, poor working memory, distractibility, internal restlessness and impulsivity. These symptoms were assessed during treatment to determine how effective the treatment was.

ADHD treatment mostly included stimulants: mixed salts amphetamine (Adderall XR), sustained release methylphenidate (Concerta – a drug similar to Ritalin), or sustained release dextroamphetamine sulphate (Dexedrine spansules). In general, mixed salts amphetamine was offered first and the dose gradually increased until clinically effective.

If this treatment was not tolerated another of the stimulants was used. In some cases, individuals were given two stimulants together; a non-stimulant drug (atomoxetine) because there were residual anxiety symptoms or some participants continued to take a combination of atomoxetine and a stimulant.

Participants attended a clinic every three to four weeks after their medication had been stabilised. Their weights were measured at the second clinic visit, which was about three months later when ADHD diagnosis was confirmed, and at their most recent clinic visit (the study ended in February 2008). Eleven participants on the control group were no longer visiting the clinic and weight was assessed by telephone. Participants’ heights were also measured at the clinic.

What were the results of the study?

Many of the 78 participants of the study had other conditions as well as obesity and ADHD, these included sleep apnoea (56%), binge eating disorder (65%) and mood disorder (88%).

At their second weighing (at the time of diagnosis of ADHD and before starting treatment) the treated and control participants had similar BMIs of around 43 in the treated group and about 42 in the control group.

By their final weigh in, people treated with ADHD medication lost on average about 12% of their body weight (about 15kg), while the controls gained an average of about 3% of their body weight (about 3kg).

What interpretations did the researchers draw from these results?

The researchers concluded that ADHD is highly prevalent in severely obese people with a history of weight loss failure, and that treating these people with ADHD medication results in significant long-term weight loss.

The researchers say that, “ADHD should be considered as a primary cause of weight loss failure in the obese.”

What does the NHS Knowledge Service make of this study?  

This was a small study with a number of limitations. For example, the process for selecting controls was poor:

  • The people used as control subjects were those who did not want to take ADHD medication, stopped treatment due to adverse effects with the medication, or stopped treatment because the medications did not provide ‘clear benefit’. It was unclear exactly how ‘clear benefit’ was defined, whether it referred to benefit for symptoms of ADHD or benefit in terms of weight loss.
  • The group who adhered to treatment may have been more committed to losing weight than the “control” group: this is supported by the fact that 11 of the 13 controls discontinued clinic visits before the end of the study.
  • The groups are also likely to have differed in other factors that could have contributed to the difference in weight loss seen. Ideally, individuals would be randomly assigned to receive either treatment or a placebo. This would ensure that the groups were evenly balanced and identify the true effect of the drug.

There were a number of further limitations, including:

  • The diagnosis of adult ADHD was made using a number of standard scales but also involved clinical interviews conducted by the study team. Therefore, some level of professional judgement by the authors was involved, which may mean that different professionals may come up with differing diagnoses. An independent assessment and verification of the diagnosis of ADHD would have    been preferable.
  • The lack of any placebo treatment group means that it is impossible to say how much of the weight loss was due to the ‘placebo effect’, that is, weight loss not attributable to the effects of the medication, but due to the fact that participants knew they were receiving a treatment that should help them lose weight. In addition, treatment of weight-related conditions, dietary intervention and activity counselling could also have contributed.
  • The treatment of ADHD involves psycho-stimulants, such as amphetamines. Amphetamines have long been known to induce weight loss, not just in people with ADHD. However, this practice has largely been discouraged due to the side effects of these drugs. Misuse of amphetamines can lead to dependence, and is associated with a risk of serious cardiovascular events, including sudden death. The weight loss effects of the amphetamines may not be related to their effects on ADHD but by other mechanisms, for example, by increasing alertness and therefore activity.
  • Most of the participants in this study (57%) used the mixed salts amphetamine (Adderrall XR). In the UK, methylphenidate (ritalin) is the more usual treatment for ADHD and Adderall is not available. As only three of the 65 treated patients in this study took methylphenidate, the relevance of this study to UK practice is questionable.
  • The study included a very specific set of individuals, those with severe obesity who had failed to achieve weight loss in the past, and who had also been diagnosed with ADHD. It is not suggested that ADHD treatment should be given to those without ADHD.

Other studies in different settings are needed to confirm the researchers’ results on how common ADHD actually is within severely obese people, who have not responded to previous weight loss treatment.

In addition, if a high prevalence is confirmed, the use of ADHD treatment for supporting weight loss in people with both severe obesity and ADHD will need to be confirmed in randomised double blind placebo-controlled trial.

Based on this study, it is too early to suggest that ADHD is a ‘primary cause’ of weight loss failure or that ADHD medication will help solve the obesity crisis.

NHS Attribution