Breaking News
January 16, 2019 - Questions to ask your doctor about post pregnancy care: MedlinePlus Medical Encyclopedia
January 16, 2019 - Neurons with good housekeeping are protected from Alzheimer’s
January 16, 2019 - Is mindfulness worthy of all the hype?
January 16, 2019 - Physical Activity, Any Type or Amount, Cuts Health Risk from Sitting
January 16, 2019 - New understanding in the evolution of human feet
January 15, 2019 - AHA: New Cholesterol Guidelines Put Ethnicity in the Spotlight
January 15, 2019 - Different brain areas linked to smoking and drinking
January 15, 2019 - Henry Marsh shares insights into neurosurgery and more at Dean’s Lecture Series
January 15, 2019 - Want to Live Longer? For Just 30 Minutes a Day, Do Anything Else But Sit
January 15, 2019 - The Current issue of “The view from here” is concerned with Targets
January 15, 2019 - Plain packaging sparked tobacco price rises, new study finds
January 15, 2019 - Sedentary lifestyles can be unhealthy, physical activity can lower risk
January 15, 2019 - Gut microbiome may help prevent development of cow’s milk allergy
January 15, 2019 - Lesbian, gay and bisexual individuals more likely to suffer severe substance use disorders
January 15, 2019 - New England Journal of Medicine Publishes Positive Results of the Pivotal Trial of Cablivi (caplacizumab) for Rare Blood Clotting Disorder
January 15, 2019 - Levels of inflammatory marker (CRP) linked to housing type and tenure
January 15, 2019 - Three gifts I’m glad I gave myself in 2018
January 15, 2019 - Columbia’s Pediatrics Department Names New Vice Chairs, Expands Leadership
January 15, 2019 - US FDA Accepts Regulatory Submissions for Review of Tafamidis to Treat Transthyretin Amyloid Cardiomyopathy
January 15, 2019 - Staying fit can cut your risk of heart attack by half
January 15, 2019 - Vitamin D supplements are of no gain to those over 70, study shows
January 15, 2019 - Scientists create comprehensive new method to predict breast cancer risk
January 15, 2019 - Research shows connection between social media use and impaired risky decision-making
January 15, 2019 - FDA Approves Expanded Use of Adacel (Tdap) Vaccine for Repeat Vaccination
January 15, 2019 - Treating spinal pain with replacement discs made of ‘engineered living tissue’ moves closer to reality
January 15, 2019 - Providers Walk ‘Fine Line’ Between Informing And Scaring Immigrant Patients
January 15, 2019 - Outcomes Poorer for Medicaid Beneficiaries With STEMI
January 15, 2019 - Decorative Products on Foods Can Be Unsafe
January 15, 2019 - A dream of sustainable surgery in Uganda
January 15, 2019 - Study shows how herpes viruses and tumors have learned to manipulate the same ancient RNA
January 15, 2019 - Common Heart, Diabetes Meds May Help Ease Mental Illness
January 15, 2019 - Stress and trauma in earliest years linked to reduced hippocampal volume in adolescence
January 15, 2019 - Scientists identify endogenous activator of sigma-1 receptors in human cells
January 15, 2019 - MAR treatments unlikely to be cause of premature or low birth weight babies
January 15, 2019 - Parental CPTSD increases transmission of trauma to offspring of Tutsi genocide survivors
January 15, 2019 - High-fat diets shown to increase blood pressure
January 15, 2019 - New institute for food safety to be established in Netherlands
January 15, 2019 - Keele University researchers receive £2.4 million grant to help reduce overprescribing of opioids
January 15, 2019 - Synthetic compound reverses mutant p53 aggregate accumulation, study shows
January 15, 2019 - First elder care robot tested in a WSU smart home apartment
January 15, 2019 - Oxford researchers explore relationship between technology use and adolescent mental health
January 15, 2019 - From microbiome research to healthier and sustainable foods
January 15, 2019 - How coaching moms and dads improves infants’ language skills
January 15, 2019 - Precision health approach tapped to identify causes of poverty
January 14, 2019 - DNA origami can accurately measure how antibodies interact with several antigens
January 14, 2019 - Researchers identify multiple new subtypes of most common childhood cancer
January 14, 2019 - Total Fertility Rates Vary by State
January 14, 2019 - Elevated blood lead level in early childhood associated with increased risk of academic problems in school-aged children
January 14, 2019 - Superior technique identified that can block CRISPR gene editing
January 14, 2019 - Turning breast cancer cells into fat cells prevents the formation of metastases
January 14, 2019 - Review examines what influences HIV-positive patients to stay on antiretroviral drugs in Africa
January 14, 2019 - Identifying genetic factors that lead to squamous cell carcinoma
January 14, 2019 - Virtual video visits can replace office visits without compromising quality of care
January 14, 2019 - Health Highlights: Jan. 10, 2019
January 14, 2019 - Molecular hallmarks of tumor hypoxia across 19 cancer types discovered
January 14, 2019 - Scientists uncover how protein clumps damage cells in Parkinson’s
January 14, 2019 - Physician-scientist’s “indomitable spirit” prevails over personal adversity
January 14, 2019 - King’s researchers receive £1.25 million to investigate fatal eating disorder
January 14, 2019 - UCR researchers uncover how plants sense temperature
January 14, 2019 - Scientists find link between colitis and colon cancer
January 14, 2019 - New skin patch provides long-acting contraceptive protection
January 14, 2019 - Asparagine synthetase deficiency – Genetics Home Reference
January 14, 2019 - Improved stem cell approach could aid fight against Parkinson’s
January 14, 2019 - New class of sleeping pill preserves ability to wake in response to danger signals
January 14, 2019 - Cancer patients are four times more likely to commit suicide
January 14, 2019 - The human brain works in reverse order to retrieve memories
January 14, 2019 - Simple tips can lead to better food choices
January 14, 2019 - Meth’s Resurgence Spotlights Lack Of Meds To Combat The Addiction
January 14, 2019 - TARA Biosystems and Insilico Medicine collaborate to discover novel therapies for cardiac disease
January 14, 2019 - Early life stress in mice affects their offspring behavior
January 14, 2019 - Depression Tied to Worse Asthma Outcomes in Urban Teens
January 14, 2019 - Santa calorie counting
January 14, 2019 - Opiod prescriptions for pet dogs misused by their masters
January 14, 2019 - People with ASD could be better at recognizing regret and relief in others finds study
January 14, 2019 - Conducting ChIP-Seq with Low Cell Numbers
January 14, 2019 - Study explores support and social networks of family carers of people with dementia
January 14, 2019 - At Risk for an Opioid OD? There’s an App for That
January 14, 2019 - Single national electronic health record will help improve care in Canadian hospitals
January 14, 2019 - Study unearths Britain’s first speech therapists
January 14, 2019 - Study reveals nuances of racial inequalities in breast cancer prevention
What causes schizophrenia? What we know, don’t know and suspect

What causes schizophrenia? What we know, don’t know and suspect

image_pdfDownload PDFimage_print

Symptoms include delusions and hallucinations (“psychotic” symptoms), diminished emotional expression, poverty of speech and lack of purposeful action (known as “negative” symptoms), and incoherent speech and disorganised behaviour (“disorganised” symptoms). A diagnosis of schizophrenia requires at least two symptoms, including one psychotic or disorganised, to be present for at least six months. These must result in significant social or occupational dysfunction.

It is thought disruptions in brain development early in life may underlie the emergence of schizophrenia in later years. While the causes of these disruptions aren’t exactly clear, research points to several possible reasons.

Genes

Hundreds of genes have been linked to schizophrenia, but do not appear to follow typical patterns of inheritance across generations, where disorders can be predicted with confidence. Like diabetes and coronary heart disease, schizophrenia cannot be predicted from family history alone. This is because no one gene, or set of genes, has definitively been identified as causing the disorder.

Family studies do provide robust evidence of a genetic contribution. For instance, across the population, a person’s risk of developing schizophrenia is 1%. If one of their parents has the disorder, the risk increases to 15%.

Twin studies have found a 50% increase in the risk of schizophrenia in the identical twin of a person with schizophrenia. Because identical twins share 100% of their DNA, this means environmental risk factors must also be involved. We do not currently know exactly which genes interact with which environmental factors, nor the extent of these interactions.

There is also an association between the age of the father at the time the child is born and an increased risk of schizophrenia in the child. If the father is over the age of 55, the child’s risk of schizophrenia increases by 50%. This may be due to rare mutations in paternal sperm that could lead to abnormal development, or to family factors associated with having an older father.

Obstetric complications

Various obstetric complications in utero and at birth have also been identified as risk factors for schizophrenia in the offspring. Complications during pregnancy include maternal bleeding, diabetes, rhesus incompatibility (when the mother has Rh-negative blood and the fetus Rh-positive, or vice versa), pre-eclampsia and abnormal fetal growth and development.

Maternal exposure to famine during pregnancy has been linked to schizophrenia in the offspring. Complications at delivery include uterine atony (failure of the uterus to contract after delivery), lack of oxygen to the fetus and emergency caesarean.

Most of these obstetric associations are small, and other potential influencing factors weren’t controlled for. For example, exposure to maternal infections, such as upper respiratory tract and genital or reproductive infections, has been linked to schizophrenia in the offspring. If exposed to these infections, these could be the real culprits rather than the obstetric complications described above.

Exposure to infections in childhood, such as Toxoplasma gondii (a parasitic organism carried by domestic cats) and viral central nervous system infections (such as meningitis), have also been linked to schizophrenia in adulthood. Again, if exposed, these could have led to the mental illness as opposed to complications in delivery.

Immune markers

Markers of infection and inflammation are often increased in adults with schizophrenia. This means immune system dysfunction may be involved in the development of the disorder.

Drug use

Studies following people from birth to adulthood have identified cannabis use in childhood or adolescence as a likely risk factor.

These studies have adjusted for other risk factors and taken into account intoxication effects and reverse causation (that schizophrenia may cause cannabis use). They found a dose-response effect, which means the risk of psychosis increased as the frequency of cannabis use increased. Such dose-response effects provide the most robust evidence of causation.

The neurological and biological mechanisms of cannabis use are similar to those in schizophrenia, with the same neurons showing activity.

Methamphetamines, particularly ice or crystal methamphetamine, have been linked to increased risk of persistent psychosis, and not just substance-induced psychosis. Controlled amphetamine administration that triggers temporary psychosis in healthy individuals can also be blocked by antipsychotics. This further strengthens the evidence of association.

Social factors

There is solid evidence supporting the link between having experienced child abuse, or any type of abuse that includes bullying, and schizophrenia. Stressful life events in adulthood have been associated with schizophrenia too.

People living in urban areas, particularly areas with high income inequality, also show increased risk, which may be associated with social fragmentation. Both first- and second-generation immigrants show increased risk, with surprisingly greater risk seen in the second generation.

Studies have also found a greater risk of schizophrenia in ethnic minority groups living in areas of low ethnic density than those living in high ethnic density areas. These finding indicate that sustained social marginalisation, particularly from early childhood, may have greater adverse effects than migration itself.

Stress

Social stressors can lead to biological disruptions. For instance, stress increases the release of dopamine. And evidence shows people with schizophrenia have increased dopamine production and release.

Stress is also associated with dysregulation of a brain network known as the hypothalamic-pituitary-adrenal (HPA) axis, which is sensitised in people with schizophrenia.

Stress associated with being raised in a harsh environment has been linked to the emergence of an inflammatory gene expression in adolescents. And people with schizophrenia show immune system dysfunction in both the early and late stages of the disorder.

Disruption to these biological systems can cause paranoid ideas, social withdrawal and other behavioural problems. These in turn cause additional stress and further biological disruption. In time, paranoid ideas can become delusional and fixed, signalling schizophrenia, particularly in the presence of other symptoms.

While much progress has been made in identifying the potential causes of schizophrenia, most of the evidence comes from population-level studies that may or may not be applicable to a particular individual. More research is required to determine the various individual pathways to schizophrenia.


Explore further:
Scientists identify 35 genes associated with cannabis use

Provided by:
The Conversation

Tagged with:

About author

Related Articles