psychologists have also identified that not all individuals who are stressed, or go through stressful life events, develop a psychological disorder. To understand this, theorists and researchers explored other factors that affected the development of a disorder and proposed that some individuals under stress develop a disorder and others do not. As such, some individuals are more vulnerable than others to developing a disorder once the stress has been introduced. This led to the formulation of the diathesis-stress model. Genetics Stress is known to be a mast cell activator. Mast cells are long-lived tissue-resident cells with an important role in many inflammatory settings, including host defense against parasitic infection and in allergic reactions. There is evidence that "children exposed to prenatal stress may experience resilience driven by epigenome-wide interactions". Early life stress interactions with the epigenome show potential mechanisms driving vulnerability towards psychiatric illness. Ancestral stress alters lifetime mental health trajectories via epigenetic regulation. Carriers of congenital adrenal hyperplasia have a predisposition to stress due to the unique nature of this gene. True rates of prevalence are not known, but common genetic variants of the human Steroid 21-Hydroxylase Gene (CYP21A2) are related to differences in circulating hormone levels in the population. Psychological distress significantly impacts the quality of life of affected individuals. It is a known feature of generalized joint hypermobility (gJHM), as well as of its most common syndromic presentation, namely Ehlers–Danlos syndrome, hypermobility type (also known as joint hypermobility syndrome, JHS/EDS-HT). Interestingly, in addition to the confirmation of a tight link between anxiety and gJHM, preliminary connections with depression, attention deficit hyperactivity disorder (ADHD), autism spectrum disorders, and obsessive–compulsive personality disorder (OCPD) were also found. Sensory processing sensitivity (SPS) is a personality trait involving "an increased sensitivity of the central nervous system and a deeper cognitive processing of physical, social and emotional stimuli". The trait is characterized by "a tendency to 'pause to check' in novel situations, greater sensitivity to subtle stimuli, and the engagement of deeper cognitive processing strategies for employing coping actions, all of which are driven by heightened emotional reactivity, both positive and negative". SPS captures sensitivity to the environment in a heritable, evolutionary-conserved trait associated with increased information processing in the brain, moderating sensitivity to environments in a for-better-and-for-worse fashion. Interaction with negative experiences increases the risk for psychopathology, whereas interaction with positive experiences (including interventions) increases positive outcomes. Protective factors Protective factors, while