Impact of Common Mental Health Disorders on Cognition: Depression and Posttraumatic Stress Disorder in Forensic Neuropsychology Context

The assessment and diagnosis of posttraumatic stress disorder (PTSD) and depression in forensic evaluations may lack an acknowledgement of the neurocognitive impact of these disorders and how they interact with other causative factors, such as traumatic brain injury (TBI), pain or fatigue. Both PTSD and depression have a complex, growing and consolidating neuroscientific and neuropsychological evidence base, and both can affect neuropsychological test results. In forensic neuropsychological assessments, they are often considered to be confounding factors in evaluating TBI and neurodegenerative disorders but not a source of cognitive impairment in their own right. Yet, an accurate neuropsychological assessment of both cognition and affect is vital to causality determination, prognosis and treatment planning. To complicate matters, selective brain injuries, contingent on the location of injury, can produce symptoms of depression that also affect the neurocognitive profile. Therefore, behavior can overlap not only due to overlapping or comorbid diagnoses, but also due to similar neuroanatomical correlates of both conditions. This paper focuses on reviewing and integrating the available empirical evidence from neuroscience and neuropsychology regarding the cognitive impact of PTSD and depression. Our critical review will emphasize the implications of the more recent evidence for forensic assessment determinations regarding causality, diagnosis, and the impact on function, prognosis and treatment. Hence, electronic search engines, PubMed, PsycINFO, and Google Scholar (up to January 2018) were screened and reviewed both for the neuroscience and neuropsychological literature related to depression and PTSD.