reactive indicates that it is in response to an event or trauma, whereas clinical depression is quite persistent

There is a big difference between reactive depression and clinical depression.

Reactive Depression:
When a sad or distressing event occurs, one may become distraught and not be able to get past the feelings of loss. This can occur when losing a loved one, a pet, or a job. The depression that exists because of an event will heal with time. Usually talking to loved ones, change of scenery, or other positive reinforcements will enable the person who is reactively depressed to get out of the blues and back into society with no side-effects, after a period of time, between one and three months, typically.

Clinical Depression:
There are chemicals in the brain that control different moods. If there is an over-abundance or too little of some of these chemicals, such as seratonin, the feel-good chemical, or some amino acids, which help with the distribution of chemicals in the brain, then the individual who suffers can become clinically depressed. The feelings of loss come from within, and not from any situation or event. This person is sometimes so debilitated by the sadness that they are feeling that they are unable to function. This type of depression is not going to be fixed by time, because it's chemical, and not situational. One must seek out professional help in order to learn how to cope with the feelings of depression. They are likely to be prescribed a medication that will help them to balance the chemicals in their brain.

"Reactive depression" is exactly that, a reaction to a major life event. The depression usually sets in within three months of an event and is characterized by what appears to others to be somewhat of an over reaction to the event. The depression can be caused by a good or a bad event from the birth of a baby to the death of a loved one. Reactive depression usually doesn't last longer than 6 months and is treated with antidepressants, counseling, and support groups, which individually or combined enables the person to accept and cope with whatever occurred.

Clinical depression is one of the worst manifestations of depression. The depression is severe and relentless. Clinical depression is characterized by a total lack of interest, continued depression, inability to perform normal jobs or activities, thoughts of suicide, and a number of other symptoms. It's generally treated with antidepressants and counseling. For extreme cases, treatments using electrical currents or brain stimulus may be used. Treatment for clinical depression could be long term.

Reactive depression, also referred to as situational depression, is a depression disorder triggered by external events or traumas. It is diagnosed when the symptoms causing depression are not typically associated with that of clinically diagnosed depression. The symptoms will disappear within a short period of time, with a maximum of 6-8 months, after removing the person from the situational stimuli causing the anxiety and sadness.

Meanwhile, the difference between reactive depression and clinical depression is that major depression, as clinical depression is also referred to, is a serious AXIS I mental disorder (according to the DSM-IV). This is a disease that becomes pathological after a period of time, due to being untreated after traumatic events. Clinical depression significantly alters moods and impacts all behaviors in life. This is the primary difference between the two.