Many studies in an academic examination of complex PTSD indicated that complex trauma survivors—compared to trauma survivors—tend to have more frequent and intense somatic symptoms, anxiety, stress, depression, anger, unpleasant feelings, suicidal thoughts, hopelessness, loneliness, social isolation, and dissociation. In other words, most symptoms are more severe for those diagnosed with C-PTSD than PTSD.

Complex trauma survivors tend to struggle with connecting to and trusting others due to chronically being betrayed and harmed by those most expected to protect and care for them such as family or romantic partners.

Immense intellectual processing is needed for cognitive-based talk therapies. Trauma survivors, however, may struggle to think deeply when experiencing emotional dysregulation, somatic flashbacks, or traumatic triggers when trying to work through their traumas in therapy.

Trauma therapists, who specialize in somatic therapy, try to indirectly and slowly reprocess traumatic experiences, rather than directly and deliberately intensifying traumatic memories such as with cognitive therapies or EMDR therapy. Initially, many complex trauma survivors’ will need to strengthen their nervous systems with somatic therapy before being able to tolerate EMDR therapy, or for EMDR to be more effective.

In two randomized controlled trials (RCTs), which tend to be the most rigorously designed studies, somatic therapy has shown large effects for reducing trauma symptoms, and medium-to-large effects for reducing depressive symptoms.

Studies have indicated that 34.4% to 46.4% of persons diagnosed with PTSD also struggle with substance addictions. Together, trauma and addiction are associated with worse depressive symptoms.

In a meta-analysis, or a quantitative review of 9 studies examining the effectiveness of EMDR therapy with people who struggle with addiction, the researchers found that EMDR therapy was moderately effective on both PTSD and substance addictions.