Is mental illness being diagnosed correctly?

By Dr. Liji Thomas, MDOct 10 2019

An important new piece of research appearing in the journal JAMA Psychiatry questions the accuracy of current diagnostic methods used in mental illness, and the true relevance of the diagnoses to the underlying disturbances in the brain’s function.

The study is based on obsessive-compulsive disorder (OCD) and its relationship with goal-directed planning. It suggests that deficits in goal-directed planning are predicted better by self-reported compulsiveness than by the presence of an OCD diagnosis. This may help understand how brain dysfunction is related to mental illness and to evolve better diagnoses and treatments.

Image Credit: Kaspars Grinvalds / Shutterstock

Diagnosis of mental disorders the DSM way

Current definitions of mental disorder are based on the diagnostic and statistical manual (DSM) criteria, and have an on/off aspect. In other words, people who fit the criteria have the condition, otherwise, not. While this can be rationally defended when it comes to making clinical decisions with greater ease, it may overlook several vital aspects of mental health and illness due to its straitjacketed nature. The researchers call for a case-by-case approach to defining mental health conditions.

A review of existing studies shows that DSM categories may need revision, so that the diagnosis is based on clinical phenotypes, or presentations, which can be graded for severity, and are seen across a range of illnesses. For one thing, many mental illnesses show a sizable degree of overlapping signs and symptoms. Thus many patients fit the criteria for more than one disorder. Secondly, many mental illnesses have common symptoms, such as compulsive behavior. Thirdly, many disorders of the mind present in a variety of ways, that is, they have heterogeneous presentations. Thus two patients with the same illness could have hardly any similarity in the way they present, and may show quite different or opposite reactions to the same treatment.

Identifying the role of compulsiveness in OCD

Older research has shown that many mental health conditions are typified by compulsive and repetitive behaviors. A classic example is OCD, and this was used as the example in the current study.

The current study was designed around the question of whether self-reported compulsiveness or an OCD diagnosis would better detect one clinical phenotype in mental illness: the impairment of goal-directed planning. This is a term used to describe the individual’s ability to make decisions about future activity, to correctly imagine different future scenarios that may occur as a result of these decisions, and to choose decisions that are in tune with what the individual wants and needs in the current setting. The choice of this parameter was based on the availability of knowledge of brain dysfunction in this condition as well as how it responds to various drugs. Computational models have also been produced which apply across different species.

Goal-directed control is thought to protect against disruptive habit formation, such as is seen in OCD, addictions and binge-eating disorder. Impairments in this parameter are therefore not specific to OCD. This could be because compulsive behavior and intrusive thoughts occur in a wide range of diagnoses.

The study

To find out whether this trait crosses diagnostic boundaries, and how it relates to currently operating diagnoses, the researchers looked at 285 patients who had been diagnosed with OCD, generalized anxiety disorder (GAD), or both. They looked for compulsivity in all patients.

Patients with GAD do not present with compulsive behavior, or goal-directed planning impairment, as in OCD. On the other hand, it is linked to excessive worry and intrusive thoughts, both of which are found in OCD as well. These disorders also share nonspecific features like distress and functional impairment. If the researchers were able to separately identify the contribution of compulsivity from that of obsessionality and general distress, they would be able to find out how each of these could be affecting goal-directed control in OCD.

The researchers felt that the impairment of goal-directed planning in these patients would be strongly and selectively related to compulsivity, spanning all three categories of diagnosis, and that the occurrence of compulsivity would predict this deficit better than the expert-assigned diagnosis of OCD. As an extension of this study, they also predicted that higher orders of cognitive function like cognitive flexibility and abstract reasoning would show the same association because they are often linked to a diagnosis of OCD and are also part of the same neural loop as goal-directed control.

The findings and implications

The current study shows that each patient met, on average, the diagnostic criteria for 3.7 concurrent illnesses. The presence of self-reported compulsivity was a better indicator of poorer goal-directed performance and of impaired abstract reasoning. It also shows that self-reported compulsiveness relates to different facets of cognitive flexibility more accurately than the expert diagnosis does, in many cases. Cognitive flexibility refers to the brain processes which regulate habitual behavior.

Changes in these processes were more easily and correctly predicted by asking the patient about compulsive behavior rather than relying on the diagnosis of OCD. That is, OCD was not associated with impaired goal-directed control but compulsivity was. When both were analyzed together, a diagnosis of OCD had almost no effect on goal-directed planning, and neither did other factors used in the analysis such as obsessionality or general distress.

Researcher Claire Gillian says, “By defining mental health and illness in a way that is true to the biology of the brain and respects the reality that most mental illness varies in the population, it is hoped that we are charting a path towards a future where treatments can be prescribed on a more individualized basis, based on well-defined brain systems and circuits and crucially, with a higher rate of success.”