Psychiatric disorder
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Understanding Psychiatric Disorders: Definitions, Genetic Links, and Neural Mechanisms
Defining Psychiatric Disorders: Essentialist, Socially Constructed, and Mechanistic Property Cluster (MPC) Kinds
Psychiatric disorders have been conceptualized in various ways, reflecting the complexity and multifactorial nature of these conditions. Essentialist kinds, which work well for physical and some medical phenomena, are not suitable for psychiatric disorders due to their fuzzy and multifactorial nature1. Socially constructed kinds emphasize the cultural context but overlook shared physiological mechanisms1. Practical kinds, as seen in DSM nosologies, focus on utility rather than shared causal processes1. The most promising model is the Mechanistic Property Cluster (MPC) kinds, which define psychiatric disorders through complex networks of causal mechanisms, similar to biological species1. This model suggests that psychiatric disorders are objectively grounded in the causal structure of the mind/brain, with central and marginal members within each disorder1.
The Nature of Psychiatric Disorders: Realism, Pragmatism, and Constructivism
The nature of psychiatric disorders can be understood through three major theories: realism, pragmatism, and constructivism. Realism posits that psychiatric disorders are real and independent of human activities, with a better fit in biology-based realism akin to species rather than chemistry-based realism2. Pragmatism focuses on the practical utility of diagnostic categories without asserting their reality, which can be problematic for advocacy2. Constructivism acknowledges the role of social forces in diagnosis but argues that truly socially constructed disorders are rare2. The coherence theory of truth suggests that disorders become more valid as they better fit into our broader understanding of the world2.
Genetic Correlations and Shared Etiology Among Psychiatric Disorders
Genetic studies reveal significant heritability and shared genetic etiology among various psychiatric disorders. Genome-wide association studies (GWAS) have shown that common single nucleotide polymorphisms (SNPs) explain a portion of the genetic variance in disorders like schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorders, and ADHD4 6 10. High genetic correlations exist between schizophrenia and bipolar disorder, and moderate correlations between schizophrenia and major depressive disorder, as well as between bipolar disorder and major depressive disorder4. These findings suggest common pathophysiologies and encourage further investigation into shared genetic mechanisms4 6.
Neural Circuit Disruptions in Emotional Processing Across Psychiatric Disorders
Disrupted emotional processing is a hallmark of many psychiatric disorders, with common neural circuit disruptions identified across conditions. Meta-analyses of neuroimaging data reveal abnormal activation in regions such as the amygdala, hippocampal/parahippocampal gyri, thalamus, and prefrontal regions7. These disruptions correspond to key networks involved in emotional reactivity and regulation, including the "salience" network, the "reward" network, and the "nonreward" network7. These findings support the formulation of psychiatric illnesses as dysfunctions in transdiagnostic neurobehavioral phenotypes7.
White Matter Microstructural Alterations in Psychiatric Disorders
White matter microstructural alterations are common across several psychiatric disorders. Studies have shown that schizophrenia, bipolar disorder, and autism spectrum disorder share similar alterations in the corpus callosum, with additional changes in the limbic system for schizophrenia and bipolar disorder8. These findings highlight both shared and unique pathophysiological characteristics among psychiatric disorders, providing insights into their nosology8.
Conclusion
Psychiatric disorders are complex and multifactorial, best understood through models that account for their intricate causal mechanisms. Genetic studies reveal significant shared etiology among various disorders, while neuroimaging studies identify common neural circuit disruptions. These insights underscore the importance of considering both shared and unique aspects of psychiatric disorders in research and clinical practice.
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What kinds of things are psychiatric disorders?
Psychiatric disorders are objectively grounded features of the mind/brain, defined as complex, mutually reinforcing networks of causal mechanisms.
Very Rigorous Journal
Highly CitedThe nature of psychiatric disorders
Psychiatric disorders are more biology-based than chemistry-based, and should be argued for more confidently, rather than just relying on current diagnostic categories.
Highly CitedThe severity of psychiatric disorders
Severity of psychiatric disorders should be defined independently from functional impairment, as it influences decisions about care and treatment decisions.
Highly CitedGenetic relationship between five psychiatric disorders estimated from genome-wide SNPs
Shared genetic etiology exists between schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorders, and ADHD, potentially impacting nosology and promoting research on related disorders.
Observational Study
Rigorous JournalHighly CitedMentally Sick or Not—(Bio)Markers of Psychiatric Disorders Needed
(Bio)markers are needed to accurately diagnose psychiatric disorders, such as major depression, bipolar disorder, schizophrenia, and anxiety disorders, and to help determine if individuals are mentally healthy or not.
Rigorous JournalMulti-trait analysis for genome-wide association study of five psychiatric disorders
Seven genes, including SORCS3, are commonly associated with four out of five psychiatric conditions, providing new insight into the genetic basis of these disorders.
Meta-AnalysisVery Rigorous JournalHighly CitedIdentification of Common Neural Circuit Disruptions in Emotional Processing Across Psychiatric Disorders.
Neurocircuit disruptions in emotional processing networks are common across major psychiatric disorders, suggesting psychiatric illness may be formulated as dysfunction in transdiagnostic neurobehavioral phenotypes.
Meta-AnalysisHighly CitedWhite matter microstructural alterations across four major psychiatric disorders: mega-analysis study in 2937 individuals
Schizophrenia, bipolar disorder, and autism spectrum disorder share similar white matter microstructural alterations in the corpus callosum, while major depressive disorder shows no significant differences compared to healthy individuals.
Meta-AnalysisVery Rigorous JournalHighly CitedSchizophrenia, Bipolar and Major Depressive Disorders: Overview of Clinical Features, Neurotransmitter Alterations, Pharmacological Interventions, and Impact of Oxidative Stress in the Disease Process.
Oxidative stress may play a role in the pathogenesis of schizophrenia, bipolar disorder, and major depressive disorder, with potential implications for pharmacological treatments.
Literature ReviewGenomewide association studies: history, rationale, and prospects for psychiatric disorders.
GWAS have identified associations of common SNPs and rare copy number variants with psychiatric disorders, but more findings are likely and therapeutic applications require further effort.
Systematic ReviewHighly Cited