In an article published in the February issue of Psychiatry Research, Blakey and colleagues examine potential behavioral mechanisms that link depression and trauma, and investigate why trauma survivors—including those diagnosed with ( )—become depressed.1 Before examining the study’s findings, let us briefly review the criteria for PTSD and major depressive disorder.

What is post-traumatic stress disorder and how is it treated?

The diagnosis of post-traumatic stress disorder requires exposure to actual (or to threats of) injury, violence, or death; the experience of intrusive symptoms (e. ., flashbacks); attempts to avoid some internal and external cues (e.g., thoughts, location) that might trigger trauma-related distress; and negative changes in mood (like inability to feel ), (such as believing nobody is worthy of one’s trust), and arousal/reactivity (e.g., getting startled easily).2

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Treatments for PTSD include antidepressants and/or —especially cognitive processing therapy and prolonged exposure therapy.

What is major depressive disorder and how is it treated?

The criteria for major depressive disorder (or major ) include depressed mood, reduced interest in previously enjoyed activities (e.g., hobbies, work, chatting with friends), significant changes in weight and sleep, fatigue, feelings of , slowing of movements, trouble concentrating, and thoughts.2

Treatments for depression include antidepressants and/or psychotherapies—especially interpersonal psychotherapy, cognitive-behavioral therapy, and behavioral activation.

Is depression onset related to trauma?

Having briefly reviewed depression and PTSD diagnoses and treatments, let us now consider the present study. Data for this study came from the first two waves of a large survey conducted in the 2000s by the National Institute on and Alcoholism in the 2000s.

Using face-to-face computer-assisted interviews, the National Epidemiological Survey on Alcohol and Related Conditions (NESARC) was able to obtain background information and to assess drug/alcohol use and disorders in 43,093 (first wave) and 34,653 individuals.1

For the current study, using data from those who had participated in both waves, researchers created a “trauma-exposed group” (traumatized individuals with no history of depression) and a necessarily smaller “PTSD group” (those in the first group who met the criteria for PTSD).

The trauma-exposed sample included 8,301 people (41% male; average age 47 years). The PTSD sample included 1,055 people (32% male; average age 46 years).

Between the first and second wave, 9% of trauma-exposed individuals and 23% of those with lifetime PTSD developed depression.

Spearman correlations, chi-square tests, and analysis showed that onset of depression was associated with both trauma-related interference with daily living and self- with alcohol. However, only in correlational analyses was the onset of depression associated with drug use and relationship difficulties (caused by stress). These findings provide partial support for the behavioral model of depression.

The behavioral model of depression assumes, in part, that a lack of behavior-dependent positive reinforcement (e.g., rewards) results in depression.3

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Why is there a relationship between depression and trauma/PTSD?

The behavioral model of depression suggests that post-traumatic stress disorder may cause depression by reducing a traumatized person’s opportunities to obtain positive reinforcement.

To illustrate the connection between behavioral reactions to trauma and development of depression, consider the case of an individual who, while strolling through a park, is attacked and raped.

How might the victim change her behavior as a result of this trauma? She is likely to avoid certain activities and locations.

But she is unlikely to avoid only situations matching the rape incident (e.g., local park late at night). For instance, she might instead refuse to go to the park at all hours...or to go to any park no matter what time...or go out alone at night. Maybe she will also reduce her sexual activity or stop engaging in it altogether.

Others will also react (often negatively) to the changes in her behavior; she may start losing relationships with her friends because they can no longer accommodate her extensive avoidance behavior.

Therefore, trauma victims often have limited opportunities to obtain pleasure and rewarding experiences (including social support); and as the behavioral model of depression predicts, a large number will develop depression.

Other behaviors by trauma victims might further reinforce avoidance and contribute to their eventual depression. For instance, to escape distressing memories and to alleviate unpleasant physical symptoms associated with the trauma, they may resort to alcohol and drugs. This temporary relief comes at the cost of reinforcing escape and avoidance coping—as opposed to a more active and healthier approach of examining trauma-related feelings/thoughts. In addition, drinking and drugs sometimes replace other reinforcers (e.g., playing sports).

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Weakening the trauma/depression link

Given the behavioral relationship between PTSD and depression, trauma patients might benefit from behavioral treatments for depression.

Consider behavioral activation for depression, which encourages engagement in pleasurable activities and activities that promote competence and . Behavioral activation for trauma patients may work in a similar way.

Behavioral activation treatment for people with PTSD or depression may be more effective if it incorporates the patient’s values.4 Why? Because people are more prone to using “personalized” and “naturally reinforcing” and activities,1 and these include activities relevant to one’s values. For instance, a trauma survivor who self-medicates using alcohol (but not to the point of abuse) may not feel motivated to reduce this behavior for health-related reasons. However, he may feel more motivated to stop drinking if he feels that spending the weekends drinking alone disagrees with his value of “being a good parent” and spending more time with his child. Therefore, it is important to identify the patient’s values because adaptive behaviors that agree with and promote these values are more likely to be naturally rewarding and thus chosen more regularly.