Anxiety disorders (ADs) are common among patients with eating disorders. In one study of female inpatients, around 50-65% had a comorbid anxiety disorder (see my post here). Anxiety disorders in patients with anorexia nervosa (AN) typically begin before the eating disorder and often persist after weight restoration and recovery (Bulik et al., 1997; Casper, 1990). Moreover, previous twin studies have suggested that there’s a “correlation between eating disorders and certain anxiety and depressive disorders, suggesting they comprise a spectrum of inherited phenotypes” (Hudson et al., 2003; Mangweth et al., 2003).
In this paper, Michael Strober and colleagues hypothesized that anxiety disorders and anorexia nervosa share common genetic, neural, and/or behavioural mechanisms. As such, they sought to investigate the association of AN with ADs by studying the prevalence of ADs in first-degree relatives of AN patients and comparing it to the prevalence of ADs in first-degree relatives of healthy controls.
Their rationale was that,
If transmission of anxiety proneness plays a role in vulnerability to AN, it can be expected that anxiety disorders would aggregate significantly in family members of probands with this illness.
Just to note, this study only investigated the relatives of restrictive-type AN patients, and in addition to ADs, they included obsessive compulsive personality disorder (OCPD) (not to be confused with obsessive compulsive disorder (OCD)).
Here’s a table summarizing the prevalence of ADs and OCPD among relatives of AN participants and healthy controls, as well as the adjusted odds ratio.
The prevalence of OCD, generalized anxiety disorder (GAD), any anxiety disorder, and OCP was significantly higher among first-degree relatives of AN patients than healthy controls. Indeed, first-degree relatives of AN patients had a 3 times greater risk of having OCD, GAD, and OCPD, and a moderately elevated risk of panic disorder, social phobia, separation anxiety and simple phobia.
When the authors controlled for the fact that relatives of AN patients have a higher risk of full or partial EDs, they still found that GAD and OCPD were much more prevalent among relatives of AN patients than controls (p<0.001 for the nerds).
There are several limitations to this study, but the main one, I think, is that the authors screened for psychiatric illnesses in the healthy control participants, and in doing so, they might have increased the apparent association between ADs and AN.
The authors went on to speculate about what these findings might mean for the pathophysiology of AN and the implications for nosology (classification) of AN.
Specifically, the authors hint at the idea of potentially classifying AN under ADs. (“The findings also invite speculation on a possible nosological relationship of AN to anxiety states.”) I am not sure how I feel about that, although I do think there are a lot of similarities. Mainly, though, I need to read more about this topic to formulate an educated opinion. (And there are lots of papers, here’s a relatively recent one, for example, which is freely available to the public.)
On how anxiety disorders and anorexia nervosa might be linked on a genetic and neurobiological level, Strober et al. wrote:
Given that persons with behavioral inhibition, aversion to novelty, and neuroticism (traits which, as noted earlier, occur premorbidly in AN) are prone to low self-regard and thus experience higher than normal levels of perceived stress, these findings collectively support the intriguing possibility that vulnerability to AN is expressed neurodevelopmentally; specifically, that risk unfolds in a manner that is dynamic and progressive, involving a heritable inclination to extreme anxiety and fear, and then compromise of emerging cognitive and affective processes by corticolimbic circuitry that is, in effect, ‘‘locked’’ in a state of chronic activation by life events that are perceived and experienced by these temperamentally ‘‘at risk’’ children as uncomfortably novel and anxiogenic.
The authors concluded with a question, “Importantly, what factors contribute uniquely, or selectively, to weight and shape concerns among those who are anxiety prone?”
Readers, what are your thoughts on this?
By the way, ELT makes her case for anorexia being an anxiety disorder “with a specific set of rules” in her guest post on Charlotte’s blog (Anorexia Nervosa: An Anxiety Disorder with a Specific Set of Rules?). I urge readers to check it out, ELT’s experiences are–while not unique–under-represented when we talk about eating disorders and eating disorder causes (particularly in the mainstream media).