~ Comorbidity in anxiety disorders refers to the simultaneous presence of two or more anxiety disorders (anxiety-anxiety comorbidity) or one anxiety disorder and one depressive disorder (anxiety-depressive comorbidity).

~ Comorbidity in anxiety disorders is the rule, not the exception

~ Anxiety-anxiety comorbidity and anxiety-depressive comorbidity occur at the same frequency.

~ Certain socioeconomic and personality traits are a risk factor for anxiety comorbidity

~ Anxiety-anxiety comorbidity is more chronic, while anxiety -depressive comorbidity is more incapacitating.

Comorbidity is a term referring to the simultaneous presence of two or more diseases, including psychiatric disorders. For example, studies show that the proportion of individuals who exhibit comorbidity in psychiatric disorders is about 50%, but more importantly anxiety and depressive disorders have the highest prevalence rate of comorbidity.

In fact, comorbidity in anxiety disorders is expected to occur rather than being an exception, and this includes anxiety- depressive comorbidity (anxiety and depression), anxiety-anxiety comorbidity (two different types of anxiety disorders, typically social anxiety and another anxiety disorder), and even double comorbidity which implies the presence of two anxiety disorders and one or two depressive disorders.

Factors in Anxiety-Anxiety Comorbidity

Evidence shows that anxiety-anxiety comorbidity occurs as frequently as anxiety-depressive comorbidity, but it has an earlier age of onset (i.e., age at which the comorbid disorder first appears) and is more chronic. Incidentally, it was found that there are no clinical differences between a comorbidity in which depression comes first or one in which anxiety develops first. 

Furthermore, anxiety-anxiety comorbidity is frequently observed in individuals who experienced a childhood trauma, are low in extroversion (i.e., more introvert than extrovert) and have higher levels of neuroticism. By contrast, anxiety-depressive comorbidity is more common in women, individuals who are unattached, have a neurotic personality, a low social status and low educational level.

Interestingly, individuals with anxiety -anxiety comorbidity report experiencing more severe anxiety and depressive symptoms than those with a single anxiety disorder, which suggests that symptoms in this type of comorbidity are more severe.

Additionally, comparing the two types of anxiety comorbidity, we find that anxiety-depressive comorbidity results in more social difficulties (i.e., low social functioning such as not being able to hold down a job, having a social life, etc..) while anxiety-anxiety comorbidity is characterized by a more chronic course.

Finally, evidence indicates that neuroticism represent a high risk factor in both types of anxiety comorbidity. Specifically, neuroticism characterizes individuals who have a natural disposition towards negative affect, particularly anger, anxiety, irritability, emotional instability and depression.
These characteristics suggest that a neurotic person could be more vulnerable to developing an anxiety or a depressive disorder since anxious and depressive feelings underlie this personality trait.

Hofmeijer-Sevink MK, Batelaan NM, van Megen HJ, Penninx BW, Cath DC, van den Hout MA, van Balkom AJ. Clinical relevance of comorbidity in anxiety disorders: a report from the Netherlands Study of Depression and Anxiety (NESDA). J Affect Disord. 2012 Mar;137(1-3):106-12. doi: 10.1016/j.jad.2011.12.008. Epub 2012 Jan 10. PMID: 22240085.


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