Is Anxiety Always Linked to Depression?

Anxiety is a collective term for a number of subtypes that include generalised anxiety disorder, social anxiety, panic disorder, specific phobias and substance abuse anxiety (1). The key factors involved in anxiety disorders are excessive fear and worry. Although there are different subtypes of anxiety disorder, scientist believe that they are very similar in that they recruit essentially the same neuroanatomical and neurochemical substrates. The difference lies in the way these malfunctions are manifest clinically. Thus, for example, general anxiety disorder manifests as persistent fear and worry, whereas panic disorder manifests as persistent worry with intermittent fear (1).

On the other hand, depression is a disorder of mood and is characterised by symptoms that include feelings of sadness or emptiness (low mood), anhedonia (loss of enjoyment), pessimistic thoughts, guilty recollections, suicidal ideas, changes in sleep patterns (usually insomnia), early morning waking, difficulties with concentration, forgetfulness, loss of appetite and reduced energy (1).

Both anxiety disorders and depressive disorders can exist as clinical conditions on their own and it has been found that different central substrates are involved in these two disorders (1). However, about 50 – 60% of the individuals who are diagnosed with depression are also diagnosed as having an anxiety disorder. Interestingly, both depression and anxiety disorders can be treated with drugs developed originally for depression, such as the SSRIs (Specific Serotonin Reuptake Inhibitors). While it is not clear why depression and anxiety often coexist, a number of possible reasons have been mooted: (a) Both depression and anxiety disorders can be triggered by external stressors; (b) the central mechanisms involved in both disorders may interact in some way so that one disorder may trigger the other or vice versa; (c) these disorders have many overlapping symptoms, for example changes in sleep patterns, so that an individual may meet the criteria for both diagnoses; (d) more recently scientists have found 676 genes associated with either depression or anxiety and 509 of these genes were involved in both disorders (2). Therefore there may be a genetic link between these two disorders and this may be responsible why over half of the individuals diagnosed with depression are diagnosed with an anxiety disorder.

In summary, anxiety and depression can exist as separate psychiatric conditions, but over half of the individuals diagnosed with depression may also show symptoms of anxiety, or vice versa.

(1) Ebenezer, I.S. (2015) Neuropsychopharmacology and Therapeutics. John Wiley and Sons Ltd., Chichester, U.K.

(2) Thorp, J. G. et al. (2021) Symptom-level genetic modelling identifies novel risk loci and unravels the shared genetic architecture of anxiety and depression. Nature Human Behaviour, 5 1432-1442.