Rethinking mental illness — and health

Featured in CAMH Discovers Quarterly, Fall 2018 Edition

CAMH’s Dr. John Haltigan is searching for why some of the most hard-to-treat or pervasive mental illnesses – from autism spectrum disorder to depression — occur among children and young people. To find answers, he’s advancing novel approaches that have the potential to substantially change what we define as mental illness and mental health.

His work is part of a larger movement to break apart the existing definitions of mental illnesses into their underlying components — in other words, into the symptoms, behaviours and biological factors associated with mental illnesses – then organize them in new ways that address the realities of how people experience mental illnesses.

By developing and testing these new models, researchers seek to uncover the answers that have largely eluded science to date about the potential underlying origins of mental illnesses and how to prevent or treat them effectively. 

“The approach to defining mental illnesses to date has been a categorical approach – for example, a collection of symptoms grouped into a category we call ‘depression,’” says Dr. Haltigan, Scientist in CAMH’s Cundill Centre for Child and Youth Depression. “While the categorical approach has been important for diagnosing mental illnesses, there are a number of limitations with this way of looking at and defining mental health.” 

The standard approach defines illnesses as though they are discrete entities, says Dr. Haltigan, but many – if not most – common symptoms occur in multiple disorders. This may explain why certain illnesses, such as depression and anxiety, co-occur in some people. As well, among people with a single categorically defined mental illness, there can be a wide variation of symptoms.

The new approach views symptoms and behaviours as traits along a continuum. In this way, traits are seen to be not just part of mental illnesses, but part of broad mental health in all individuals.

“Each person may exhibit varying degrees of a trait, from none at all to low levels to high levels – there’s a continuous distribution across the population,” explains Dr. Haltigan. “Traits become a problem when they cross a threshold and impair daily life.” For example, every person may be impulsive at times, but extreme impulsive behaviour may lead to mental and physical health risks.

In this new, dimensional approach, the focus is not on illness, but on impairment. The question is: At what level of a trait, or combination of traits, does a person’s optimal day-to-day living or functioning become clinically impaired?

Identifying these thresholds requires studying large population samples. Then, mathematical weightings are determined for individual points along the continuum. In the long term, research into a dimensional approach could set defined thresholds for early intervention and better targeted treatments, says Dr. Haltigan.

Worldwide, the work of determining these thresholds is at early stages. To advance this field, Dr. Haltigan and co-investigators examined for the first time the effectiveness of two dimensional approaches in children and adolescents. Published in June 2018 in the Journal of the American Academy of Child & Adolescent Psychiatry, the study showed that both approaches provide meaningful measures of child and youth mental health symptoms, such as anxiety, conduct problems, attention problems and thought disturbances.

Dr. Haltigan is also part of the Hierarchical Taxonomy of Psychopathology (HiTOP) Consortium, a group of 70 researchers worldwide collaborating to develop quantitative, dimensional measures related to mental health.

Another aspect of Dr. Haltigan’s research is looking at functioning from the perspective of life history, an evolutionary approach that assesses how individuals and species adapt to their environment. 

For example, a child who grows up in a harsh or unpredictable environment may develop heightened vigilance, or be highly alert to changes in their environment, but appear to be inattentive in class, says Dr. Haltigan. “This behaviour has a functional basis, and is not necessarily deviant,” he says.

In a new study, he will investigate if traits in young people with autism spectrum disorder, attentive deficit/hyperactivity disorder or obsessive-compulsive disorder correspond with what are thought to be different life history profiles.

“In the West, we typically view disorders as problematic,” says Dr. Haltigan. “But if we look at them from a life history perspective, we may be able to identify a functional basis for behaviours we perceive as disorders. This could provide new ways of understanding and treating mental illness in children and adolescents.”

Dr. Haltigan is also a researcher in the Margaret and Wallace McCain Centre for Child, Youth & Family Mental Health and the Slaight Family Centre for Youth in Transition at CAMH.