The Role of Childhood Trauma in Schizophrenia
Author’s Note:
As a fourth-year undergraduate student studying Psychology and Sociology, Kara has many interests in the realm of psychology and the interrelation of psychological issues and social problems. Kara is one of the founding board members and senior editors of The Aggie Transcript: Psychology and has experience working in the field of clinical psychology and conducting research in developmental psychology. Kara is particularly interested in understanding the ways in which childhood maltreatment and trauma relate to adult psychopathology. After learning about Schizophrenia in the context of abnormal psychology and social issues, Kara became curious about the etiology and treatment of the disorder, which led her to conduct a literature review. Through this review, Kara hopes to raise awareness of the consequences of childhood trauma and inspire new ways to assess and treat Schizophrenia.
The Role of Childhood Trauma in Schizophrenia
Schizophrenia is a psychotic disorder that causes individuals to experience various distortions of reality, including hallucinations and delusions, and impairs daily functioning (American Psychiatric Association, 2013). Developing throughout one’s childhood and adolescence, the onset of this disorder typically appears in young adulthood. Multiple studies have shown that individuals with Schizophrenia usually have a history of trauma (Larsson et al., 2013). Some studies assert that Schizophrenia is a neurodevelopmental disorder caused by the interaction of defective genes and adverse environments (Popovic et al., 2019). Overall, research supports the assertion that adverse childhood experiences, especially trauma and maltreatment, are highly influential factors in the development of Schizophrenia. These factors, which can be mediated by a heritable predisposition, contribute both to the development of Schizophrenia in general, and to individual differences in each person’s condition. However, finding an exact causal connection between trauma and Schizophrenia has proven difficult. This paper serves as a review of the current literature connecting childhood trauma with Schizophrenia to examine the plausibility of a causal link.
The Role of Trauma
Childhood trauma, an extreme form of stress and adversity, is a primary risk factor in the development of Schizophrenia. This essential experience can physically alter brain development, impair cognitive processes, and hamper overall functioning (Morvked et al., 2020; Popovic et al., 2019). Popovic et al. (2019) asserted that the neural diathesis-stress model demonstrates how trauma can play a causal role in Schizophrenia. The neural diathesis-stress model is a psychological theory that explains the development of certain disorders as a result of an interaction between predisposed vulnerabilities and life stress. This theory suggests that the development and trajectory of Schizophrenia result from psychosocial stress and adverse experiences, such as childhood trauma, interacting with an existing personal or genetic vulnerability. Some support for this assertion comes from their findings that childhood trauma and psychotic symptoms were positively correlated. A study conducted by Spence et al. (2006) revealed that the more severe one’s trauma was, the more severe and persistent one’s symptoms were. This study asserts that psychosis, in general, can be a reaction to trauma.
Impacts of Specific Childhood Traumas
Different traumatic experiences have different impacts on individuals’ lives and the development of their Schizophrenia. Numerous studies have concluded that across genders, emotional neglect is the most frequent type of childhood trauma experienced by patients with Schizophrenia (Isvoranu et al., 2016; Larsson et al., 2013). Some studies have also suggested that emotional neglect may relate to thought distortions, paranoia, and disorganization (Grindey & Bradshaw, 2022; Popovic et al., 2019). Grindey & Bradshaw (2022) found that neglect in general was related to certain positive psychotic symptoms (distortions or exaggerations of normal functions; the presence of atypical perceptions or behavior). The most common positive symptoms associated with neglect were delusions of reference (the belief that neutral stimuli or the behavior of others relate to oneself) and delusions of persecution (the false belief that others want to cause personal harm) (Startup et al., 2009). However, findings across studies have not all been consistent; although emotional neglect seems to be the most prevalent type of childhood trauma, its precise role in the progression of Schizophrenia has not been concluded.
Physical abuse and sexual abuse are the most common types of childhood trauma after emotional neglect and play significant roles in the way psychotic symptoms of Schizophrenia are expressed. Varied impacts of particular types of childhood trauma often become apparent in individuals’ varied expressions of psychosis. For example, a study by Read et al. (2005) found that physical and sexual abuse appear to have positive relationships with the extent and severity of hallucinations. Furthermore, the longer the abuse lasted, the more likely individuals were to suffer from increased thought distortion as well. Additional studies have found more specifically that rape is associated with auditory hallucinations, whilst physical abuse is associated with visual hallucinations (Grindey & Bradshaw, 2022). Similarly, witnessing violence or being a victim of physical abuse is positively correlated with paranoia and poor impulse control (Grindey & Bradshaw, 2022; Isvoranu, 2016). Many studies have agreed that certain traumatic experiences consistently correlate with distinct psychotic symptoms.
Read et al. (2005) suggested that not only do different types of trauma contribute to different symptoms of Schizophrenia, but the nature of specific traumatic experiences contributes to individualized expressions of symptoms. For example, they discovered that amongst individuals who experienced childhood abuse, auditory hallucinations with malevolent voices were most common for those who grew up with an overprotective paternal figure. Read et al. (2005) also found that sexual delusions were more prominent in victims of incest than in other forms of child sexual abuse. These findings clearly link unique traumatic events, rather than general subtypes of trauma, with specific psychotic symptoms. The relationship between specific experiences and symptoms provides support for the argument that there is a direct connection between traumatic experiences in childhood and the development of Schizophrenia.
Trauma and Brain Structure
Childhood trauma impacts the structure and development of the human brain and can stunt brain growth, playing a role in the development and expression of Schizophrenia. One indicator of impeded brain development is the volume of gray matter and of the hippocampus, which are reduced in the brains of individuals with Schizophrenia and in the brains of individuals with histories of severe trauma (Popovic et al., 2019). This abnormality has been attributed to trauma, as similar development has been noted in the brains of individuals with Post Traumatic Stress Disorder (PTSD). PTSD develops as a result of facing a traumatic experience and involves re-experiencing one’s trauma in the form of hallucinations and episodes of dissociative flashbacks (American Psychiatric Association, 2013). Such symptoms are frequently experienced in psychosis, suggesting that trauma relates to psychotic symptoms (Read et al., 2005). The effects of trauma seen in PTSD have been studied more extensively than the effects of trauma in relation to psychosis. However, more studies are beginning to investigate the role of trauma in psychosis by utilizing findings from studies about PTSD and other trauma-related disorders (Read et al., 2005).
Analyses of the brains of people who have Schizophrenia and of people without Schizophrenia who experienced childhood trauma show functional irregularities. One such irregularity is the faulty functioning of the Hypothalamic-Pituitary-Adrenal (HPA) axis, the brain’s stress pathway (Popovic et al., 2019). This finding is consistent across individuals with Schizophrenia. Faulty functioning of the HPA axis leads to excessive dopamine release and other abnormalities (Jentsch et al., 2014). Such functioning is perceived to be a result of trauma, as similar HPA axis activity is evident in individuals who suffer from trauma disorders (Popovic et al., 2019). However, these abnormalities have greater impacts on individuals with Schizophrenia than those with trauma disorders; in Schizophrenia, issues caused by this impairment are more pronounced and harmful because they can trigger the onset of psychosis.
One way trauma impairs the functioning of the HPA axis and influences Schizophrenia is through the overstimulation of D2 receptors. D2 receptors are a type of dopamine receptor in the brain that receive input from the HPA axis and are needed to control impulsivity and regulate behavior (Jentsch et al., 2014). When stressful experiences activate the HPA axis of individuals with Schizophrenia, their increased dopamine release overstimulates D2 receptors. This phenomenon has been hypothesized to influence the disordered physiological processes of Schizophrenia (Popovic et al., 2019). Evidence of the influence that this process has on Schizophrenia can be seen by the antipsychotic effects that dopamine receptor antagonist drugs have on individuals with Schizophrenia (Popovic et al., 2019). Dopamine receptor antagonist drugs block D2 receptors, countering the effect of excess dopamine flooding the receptors, and decreasing symptoms of Schizophrenia. This finding suggests that increased dopamine released by triggering a faulty functioning HPA axis may explain how trauma's structural impact on a developing brain influences Schizophrenia.
The Brain and Social Functioning
Faulty functioning in the HPA axis, as a result of trauma, adversely impacts the brain’s ability to respond to stress and appropriately release the stress hormone cortisol. Such impaired functioning likely prohibits individuals with untreated Schizophrenia from behaving with adherence to norms in social interactions, even when they are not in the midst of a psychotic episode. Some common aberrant social interactions include withdrawing from interpersonal encounters, struggling with social role functioning, and exhibiting abnormal cortisol responses to social stimuli (Popovic et al., 2019). Abnormal cortisol responses become especially apparent when people with Schizophrenia encounter stressful social situations. In such situations, neurotypical brains will release a greater amount of cortisol than they do in a neutral state. However, when individuals with Schizophrenia are in stressful situations, their brains have a blunted cortisol response, failing to release as much cortisol as an unimpaired brain would (Popovic et al., 2019). Thus, childhood trauma impacts the brains of individuals with Schizophrenia in a way that prevents them from responding to social interactions typically, leading to impaired social functioning.
In addition to displaying atypical behavior in social settings, individuals with Schizophrenia have difficulty engaging in interpersonal communication. Spence et al. (2006) found a significant negative correlation between Schizophrenia and communication skills, which was especially strong for individuals who reported experiencing trauma in their childhoods. Such findings suggest that experiencing trauma as a child specifically depletes intercommunication functioning. Evidence of these impaired intercommunication skills can be seen in word-generation tests, which reveal that individuals with Schizophrenia are hindered in their ability to plan and initiate activities (Liddle, 2000). These findings provide support for the notion that individuals with Schizophrenia have more issues managing social interactions and can help explain some of their defiance of social norms. Childhood trauma, therefore, directly contributes to symptoms of Schizophrenia that impair social functioning.
Cognition
Individuals with Schizophrenia have hindered cognitive functioning, which is amplified by trauma. Morvked et al. (2020) found that there is a positive relationship between childhood trauma, cognitive impairment, and Schizophrenia, together. In a study conducted by Morvked et al. (2020), individuals with Schizophrenia scored lower on all cognitive tests they were given than individuals without Schizophrenia did. Further studies have concluded that Schizophrenia especially impairs working memory, attention, verbal learning, and general executive functioning (MacKenzie et al., 2018). These findings suggest that the decrease in cognitive abilities that may result from childhood trauma and its influence on the brain is amplified in Schizophrenia.
Support for the notion that cognitive functioning is impaired by Schizophrenia or psychosis comes from the finding that antipsychotic medication, which decreased psychotic symptoms, appeared to improve cognitive functioning (Morvked et al., 2020). Some studies have also found that certain cognitive deficits in Schizophrenia are related to specific types of symptomatology. For example, one study revealed that as negative symptoms improved when individuals with Schizophrenia began taking second-generation antipsychotics, processing speed also improved (MacKenzie et al., 2018). Evidence that antipsychotic medications, which decrease symptoms of Schizophrenia, improve cognitive functioning indicates that the disorder impairs cognition, which is impaired to a greater extent in individuals who experienced childhood trauma.
Epigenetics
Beyond the influence of trauma, Schizophrenia has a heritable genetic component. Popovic et al. (2019) assert that since childhood trauma is just one contributing factor, the development of the disorder may really be the result of gene-environment interaction. Schizophrenia could result from the cumulative effect of childhood trauma and genetic predispositions. One of the sources leading to this conclusion by Popovic et al. (2019) was twin studies. Their review of a meta-analysis explained that twin studies have shown that Schizophrenia could be 60-80% heritable. Genetic and twin studies have found that individuals who had close biological relatives with Schizophrenia were more likely to develop Schizophrenia than those who did not, even if they were raised apart from affected family members (Owen et al., 2005). For example, monozygotic twins with a relative who has schizophrenia have roughly the same concordance rates (~80%) of developing the disorder, whether they are raised together or separately (Owen et al., 2005). However, not all relatives of individuals with Schizophrenia will develop the disorder, further supporting the notion that Schizophrenia is unlikely to result from genetics alone. Most individuals with Schizophrenia have both a history of trauma and a genetic predisposition, suggesting that neither factor has a strong enough impact alone to cause the disorder (Popovic et al., 2019).
Implications
Understanding how Schizophrenia develops and relates to childhood trauma has clinical implications. Schizophrenia is a serious, often debilitating, illness that impacts people across the globe and lacks fully effective treatments. The National Institute of Mental Health reports that .33% to .75% of all non-institutionalized people have Schizophrenia. This disorder is one of the top 15 causes of disability internationally and has a high suicide rate; roughly 4.9% of all individuals with Schizophrenia die by suicide. In addition to devastating personal consequences, Schizophrenia is associated with the highest social and economic costs of all mental illnesses (Popovic et al., 2019). Individuals with this disorder may be more likely to come into contact with the criminal justice system and social services as a result of potentially harmful acts committed while in a delusional or paranoid state. Harmful acts may include violence or theft, resulting in high economic costs (U.S. Department of Health and Human Services, n.d.). In addition to the cost of legal and social services, Schizophrenia leads to increased healthcare and societal costs, including a loss of productivity. Only 20% of people with Schizophrenia are capable of working in the primary labor market and contributing to society financially (U.S. Department of Health and Human Services, n.d.; Popovic et al., 2019). The consequences of Schizophrenia extend far beyond any one impacted person, they influence society at large, making the treatment of this disorder a social interest.
Greater knowledge about the roots of the disorder will help psychologists understand their patients more and develop targeted treatments that will utilize trauma-informed care and address core causes of distress (Grindey & Bradshaw, 2022). There do not currently appear to be any treatments widely successful in helping individuals with Schizophrenia. The necessity of creating a comprehensive treatment that will help individuals manage their Schizophrenia better is apparent in the aforementioned personal and social consequences of the disorder. Understanding the etiology of Schizophrenia and the role that childhood trauma plays can aid the development of clinical interventions to prevent the illness from developing in susceptible young people. If clinicians are able to identify those at high risk, they may be able to take appropriate measures to support them and reduce their likelihood of developing the disorder. Sallis et al. (2021) concluded that in order to assist and protect individuals prone to developing Schizophrenia, traumatic experiences should be addressed immediately via therapeutic treatment. Being aware of the factors that lead to the development of Schizophrenia, especially in relation to childhood trauma, can allow individuals to get help before their disorder fully establishes, or worsens.
Conclusion
Myriad studies have found that childhood trauma is a primary influential factor in the development of Schizophrenia. All literature reviewed in this analysis has supported the notion that the main form of childhood trauma that correlates with Schizophrenia is emotional neglect. Sources also agree that the severity and extent of the trauma one experiences are positively correlated with the severity of one’s psychotic symptoms. Various forms of abuse, especially physical and sexual abuse, impact symptoms in specific ways, providing support for a direct connection between trauma and Schizophrenia. Childhood trauma is an extreme form of stress, which alters the natural development of a person’s brain, causing abnormal functioning and worsened cognitive performance, chief components of Schizophrenia. Schizophrenia also has a heritable genetic component that presumably interacts with the effects of adverse childhood experiences. However, the exact impact of epigenetics on the development of this disorder has yet to be identified. More research must be done to determine the extent of the role that epigenetics plays in Schizophrenia, and the ways trauma may interact with genetic predispositions. Identifying childhood trauma as a contributing factor in the development of Schizophrenia helps us begin to understand the disorder better, raises new questions, and directs future studies and treatments.
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