Liam Davenport

June 01, 2015

GLASGOW, Scotland — Family financial difficulties in providing basic necessities in early childhood increase a child's risk of developing ADHD later on, new research suggests.

Abigail Russell, a doctoral candidate in medical studies (Child Mental Health Group) at the University of Exeter Medical School, in the United Kingdom, and colleagues found that financial difficulties more than doubled the risk for ADHD, whereas other socioeconomic indicators had no impact.

The findings, which were presented here at the 5th World Congress on Attention Deficit Hyperactivity Disorder (ADHD), suggest that factors linked to parental stress have a greater effect than material resources and thus deserve greater attention in future research.

Explaining the genesis of the study, Russell said that she had conducted a systematic review of studies that examined the impact of socioeconomic factors with regard to ADHD, but that it had not been conclusive.

She emphasized that with regard to socioeconomic disadvantage, the effects are multifactorial.

"It's measured in a whole lot of different ways, and therefore the way you measure it might actually make a difference to how it's associated with ADHD, and that could then shed light on the etiology," she told Medscape Medical News.

Cumulative Effect

To investigate further, Russell and colleagues used data from the Avon Longitudinal Study of Parents and Children, a cohort study of children born around the UK city of Bristol during 1991 and 1992.

They collated information on 8132 participants in whom a standardized diagnostic ADHD assessment was performed at age 7 years, and they used multivariate logistic regression analysis to explore the associations with various socioeconomic factors that were present at age 0 to 2 years.

The strongest predictor of ADHD was self-reported financial difficulties, such as difficulty in affording housing, clothing, or other necessities (odds ratio [OR] of ADHD, 2.23; P < .001).

Abigail Russell

Other factors significantly associated with ADHD were living in a council house/housing association house (OR, 1.84; P = .014), living with a single parent (OR, 1.70; P = .029), and maternal age at birth (OR = 0.96; P = .017).

There were, however, no significant associations between ADHD and weekly income, maternal or paternal education, or maternal or paternal employment.

Further analysis indicated that 27.8% of the association between ADHD and financial difficulties was mediated by lack of parental involvement and exposure to psychosocial adversity, including domestic violence.

"What we found that was very interesting was that the mother being depressed when the child was young wasn't a mediator in this model, which other researchers suggested would have an impact," said Russel.

Explaining the relevance of psychosocial adversity, she continued: "It isn't what it is specifically that they're exposed to, it's the cumulative impact, or the fact that they are exposed to psychosocial adversity in general, whether that's marital discord or parent substance abuse or crime, or things like that."

"We found that was a mediator in this model."

Could these findings eventually be used to identify potential ways to reduce the risk for ADHD? "Absolutely," said Russell. "What we all hear is that ADHD is very highly heritable, but there is some impact of very early life."

"If we can find ways to intervene early on, then maybe we can prevent more children going on to develop ADHD."

Complex Disorder

Carla Tiesler, PhD, from Helmholtz Zentrum München, the German Research Center for Environmental Health, Munich, Germany, who was chair of the guided poster tour, underlined the importance of research into the early-life factors associated with ADHD.

"You really have to understand the disease before you are able to treat it properly," Dr Tiesler told Medscape Medical News.

"ADHD is a disease which has various risk factors, and I think it's really important to know all the risk factors to get an overall picture of [the different] factors over the course of ADHD to be able to adequately treat the children."

There have been a number of studies in this area in recent years. How close are we to being able to tease apart these factors to get a clearer picture of which of them are indeed increasing ADHD risk?

Dr Carla Tiesler

"This is a really important question, and it's really difficult to do this, because there are so many connections between the factors," said Dr Tiesler.

"For example, socioeconomic factors are largely correlated, and there's genetic factors that have their contribution, and then there's environmental factors, with environment–gene interactions, and gene-gene interactions.... So there's many different factors."

One notable issue that was raised a number of times during the congress is that a clear-cut definition of ADHD is lacking. Does Dr Tiesler believe that accurately defining ADHD is a crucial step in being able to fully understand what is causing it?

"I think defining this disease is a very important thing, because it's not like measuring a biomarker and saying, if it's above a certain level, then that is a disease," she said.

"It's really difficult to define what is ADHD. I think this is still a process that is ongoing," Dr Tiesler concluded.

The authors and Dr Tiesler report no relevant financial relationships.

5th World Congress on Attention Deficit Hyperactivity Disorder (ADHD). Abstract P-18-003. Presented May 30, 2015.

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