PSYCHOLOGICAL STRESS

PSYCHOLOGICAL STRESS

A central paradigm in stress research is that the endocrine, immune and nervous ‘super- systems’ engage in multiple interactions during the response of the body to acute and chronic stress. Each system is also individually vulnerable and responds to defined stressors (Fleshner and Laudenslager, 2004).

In response to stress, neurohormones, neurotransmitters, neuropeptides and neurotrophins stimulate a series of adaptation responses. These typically include behavioural, cardiovascular, metabolic, endocrine and immunological changes (Viswanathan and Dhabhar, 2005, Theoharides et al., 2004); the immunological changes range from immunosuppression to inflammation (Viswanathan and Dhabhar, 2005; Jondal et al., 2004) (Figure 2). These divergent and, at times, seemingly contradictory effects reflect the dual and multifunctional role of the immune system as both a sensory and an effector organ in the stress response.

The immune system also regulates the central nervous system (CNS). Cytokines and other inflammatory mediators can signal the brain, thus, influencing behaviour and other complex body reactions. Proinflammatory cytokines (e.g. via activation of innate immunity in response to infections) can induce sickness behaviour and depressive symptoms and might aggravate stress perception (Dantzer, 2004). Several diseases have long been recognized to be triggered or aggravated by psychological stress, such as inflammatory bowel disease (Qiu et al., 1999), migraines (Theoharides et al., 2005), experimental allergic encephalomyelitis (Chandler et al., 2002) and multiple sclerosis (Mohr et al., 2004). Also, stress perception during pregnancy can trigger pregnancy complications (Blois et al., 2005; Madhappan et al., 2003).

Figure 2: Principles of the stress response. The coordinated activation and eventual downregulation of the three super-systems (the nervous, endocrine and immune systems) ensures equilibrated stress-response patterns that result in allostasis. Allostatic overload causes disequilibrium, upregulation of immune responses and disease.