Post-traumatic stress mechanisms

The mechanisms of flashbacks are probably mixed. Some cases may be similar to post-traumatic stress disorder induced by a bad trip (Paton et al., 1973). Abraham (1983) suggested that some of the visual phenomena, such as trailing and after-images, were due to failure of inhibition in visual pathways, possibly mediated in the lateral geniculate nucleus which (in the macaque monkey) contains on-off colour neurons with receptor fields similar to those described in flashbacks. The neurochemical causes of such flashbacks, which can be very disturbing, remains elusive and attempts at treatment are usually ineffective. 

Friedman, M.J. (1990) Interrelationships between biological mechanisms and pharmacotherapy of post-traumatic stress disorder. In Wolfe, M.E. and Mosnian, A.D. eds. Posttraumatic Stress Disorder Etiology, Phenomenology, and Treatment. Washington, DC American Psychiatric Press pp. 204-225. 

O Donnell, T., K.M. Hegadoren, and N. C. Coupland. Noradrenergic Mechanisms in the Pathophysiology of Post-traumatic Stress Disorder. Biological Psychiatry 50 (2004) 273-283. 

When compared with the selective serotonin reuptake inhibitors (SSRIs), mirtazapine may show an earlier onset of action (although data are currently not well established). Mirtazapine has also been found to be efficacious in the treatment of elderly patients with depression. Mirtazapine has been shown to be effective in the treatment of panic disorder, social phobia, and post-traumatic stress disorder. In one study, mirtazapine combined with citalopram in obsessive-compulsive patients induced an earlier response when compared with citalopram plus placebo. It was suggested that antagonism of presynaptic a2-adrenergic receptors does not enhance serotonin neurotransmission directly, but rather disinhibits the norepinephrine activation of serotonergic neurons and thereby increases serotonergic neurotransmission by a mechanism that may not require a time-dependent desensitization of receptors. 

Acute transient reactions characterised by numbness, feeling dazed, insomnia, impaired concentration, restlessness and autonomic arousal may immediately follow a traumatic event. Symptoms usually occur williin minutes of the stressful event and disappear within a few days. If symptoms last longer, a diagnosis of post-traumatic stress disorder (PTSD) may be made. Avoidance behaviours may occur, as may maladaptive coping mechanisms such as substance or alcohol misuse. Transient flashbacks are common, but in most cases will stop relatively quickly. The vast majority of reactions fall within this group. 

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