There are connections between anxiety and depression, but these illnesses are not the same. They often get confused for each other because they can frequently occur together. Moreover, some of the treatments for both conditions can be similar, in some cases. Still, it’s important to understand the differences between anxiety and depression before discussing their similarities.
There are numerous anxiety and depression disorders and each one can be a little different in expression. Major anxiety disorders are panic disorder, generalized anxiety disorder (GAD), posttraumatic stress syndrome (PTSS or PTSD), obsessive-compulsive disorder (OCD), and most phobias. The symptoms of anxiety are diverse and encompass shakiness, a sense of dread, tremors, panic attacks, intense feelings of worry, excess perspiration, heart palpitations, and others. The depressive disorders are major depression and bipolar disorders, and in the depressive state, symptoms include feelings of sadness, hopelessness, suicidality, inability to participate in daily life, insomnia, and others. It’s clear that symptoms of these two conditions are not that similar.
On the other hand, these conditions may often be comorbid, which means someone who is predominantly depressed could experience strong anxiety, and though less usual, someone who begins with anxiety may also become depressed. It is more common for people with depression to develop anxiety as a secondary condition, and this happens for people with depression anywhere from 10-85% of the time. The number of studies that yield different results on this issue accounts for the huge variance in statistical likelihood.
The treatments for anxiety and depression may give some clue as to why the conditions have a correlation. There are certain medications, principally selective serotonin reuptake inhibitors and selective norepinephrine and serotonin reuptake inhibitors (SSRIs and SNRIs), which have been shown effective in treating both conditions. In particular, some SNRIs, which prevent the body from using norepinephrine too quickly, seem to effectively alleviate some anxiety and are also useful for treating depression.
This makes sense, since norepinephrine is produced by the adrenal glands and is produced and consumed in higher quantities when the body has excessive fight/flight responses to things. An imbalance could cause both depression and anxiety, and lower serotonin levels may additionally create either of these conditions. It can be said both anxiety and depression are influenced by these neurotransmitters. Similarly, the two conditions may respond to certain psychotherapy treatments, especially any form of psychodynamic or cognitive behavioral therapy.
Psychopharmacological treatment or therapy methods may suggest differences between anxiety and depression. Anxiety disorders respond to fewer of the SNRIs and SSRIs, and sometimes these medications don’t work at all. More specified psychological treatment might be used for things like phobias, OCD and PTSS. PTSS could respond well to treatments such as eye movement desensitization and reprocessing (EMDR), but generalized depression that isn’t due to trauma won’t. Similarly, exposure therapy to treat phobias has little direct effect on depression, though improved quality of life might lift depression in the phobic person.