Of the clinical psychological disorders, depression is most commonly found and anxiety is second. Depression and anxiety are distinct from one another, and do present differently in people. However, it's not particularly uncommon for a person to have both a depressed and an anxious condition.

When depression and anxiety appear together, either condition can be the cause or the result of the other. A depressed person, for example, can sometimes develop agitation or anxiety, perhaps especially as their depression lingers on. An anxious person can become withdrawn or begin to feel overwhelmed by their condition, an outlook that may bring about a depressed state. If there is a more likely scenario for a lead in between the two conditions, it may be anxiety leading to depression.

The depressed state presents, usually, a reduction in one's physical expression. Depressed people are often, though not always, emotionally down and physically listless. The depressed state is not classically a state of displaced energy, a description that matches anxiety quite well. Someone depressed who suddenly displays anxiety may in fact be displaying symptoms of bipolar disorder. Bipolar disorder is marked by lethargic depression swinging to agitation, but the agitation in bipolar disorder is mania, not anxiety. The manic state typically presents extroverted, extreme, and often exceptionally strange behavior. People with anxiety aren't typically extroverted, and don't typically display especially unusual behavior.

A chronically anxious person's sense of uptight and upset can present a considerable physical drain. An extended period of chronic anxiety can lead to physical and emotional exhaustion, and under such circumstances depression may set in. People who have anxiety also tend to become withdrawn, or to self-medicate using alcohol or drugs, and both of these coping methods can and do lead to significant depression.

As with all human conditions, emotional disorders are not uniform but do have similarities. An anxious person need not develop depression, while someone with depression may go on to develop an anxious state that is not in fact symptomatic of bipolar disorder. If there is an important reflection to keep in mind it's that a case of depression or anxiety does not automatically discount the possibility of some other emotional dysfunction also being present. Distinct psychological problems can appear simultaneously.