Mental Health Disorders
A pattern of behaviour or thinking that causes significant distress or impairment in daily functioning, and that deviates from what a given culture considers normal.
Three features appear in most definitions. First, there is distress: the person experiences genuine emotional pain, not just passing discomfort. Second, there is impairment: the disorder interferes with work, relationships, or basic self-care. Third, there is deviance: the behaviour or thinking falls outside what the surrounding culture regards as typical. All three matter, because any one of them on its own is insufficient as a basis for diagnosis.
This subtopic uses anxiety as the primary example of a mental health disorder. Anxiety is characterised by excessive worry about future events, often without a clearly identifiable trigger. It is not a single condition but a family of related disorders, including Generalised Anxiety Disorder (GAD), Social Anxiety Disorder (SAD), and Obsessive-Compulsive Disorder (OCD).
Anxiety disorders are among the most prevalent mental health conditions worldwide, which makes them a useful case study for examining biological, cognitive, cultural, and environmental explanations side by side.
Biological Explanations of Anxiety
Biology shapes vulnerability to anxiety through several pathways.
Genetic factors are the most studied. A variation in the 5-HTTLPR gene, which regulates serotonin transport, has been associated with elevated anxiety. Because serotonin plays a central role in mood regulation, reduced transporter efficiency may leave individuals more reactive to stressors.
Hormonal factors are also relevant. Cortisol, the body's primary stress hormone, is chronically elevated in many people with anxiety disorders. Over time, sustained cortisol activity can sensitise the threat-response system, making anxiety more likely to persist.
Pre-existing health conditions and prolonged exposure to stressful environments can interact with these biological vulnerabilities, increasing the likelihood that a disorder develops.
Neuroimaging evidence supports a brain-based account. Chavanne and Robinson (2021) conducted a meta-analysis of 181 studies covering GAD, PTSD, social anxiety disorder, panic disorder, and specific phobia. They found consistent links between both induced and pathological anxiety and heightened activation in the left and right insula, as well as the cingulate cortex and medial prefrontal cortex. This pattern suggests that structural and functional properties of the brain are involved in anxiety, though the meta-analytic design cannot confirm that these differences cause the disorder rather than resulting from it.
A biological correlation is not a biological cause. Brain activation differences may reflect the experience of having an anxiety disorder rather than producing it.
Genetic risk also does not operate independently of environment, which is why epigenetic accounts are increasingly influential.
The biological approach has direct implications for treatment: if anxiety has a neurological basis, medication targeting neurotransmitter systems becomes a logical intervention. This will be examined in the treatment section.