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Schizophrenia and Toxoplasmosis

 

 

Parasite May Play Role in Some Schizophrenia Cases

A parasite responsible for toxoplasmosis – Toxoplasma gondii – may be involved in the cause of around a fifth of schizophrenia cases in the US. This is according to a new study published in the journal Preventive Veterinary Medicine.

Definition of schizophrenia

University of Pennsylvania researcher Greg Smith calculated that around a fifth of schizophrenia cases may be attributable toT. gondiiinfection.

The Centers for Disease Control and Prevention (CDC) estimate that around 60 million people in the US may be infected with T. gondii. Infection most commonly occurs through eating undercooked, contaminated meat, drinking contaminated water and coming into contact with cat feces that contain T. gondii.

Most people with T. gondii infection are unaware they have it; people with healthy immune systems are usually able to stop the parasite causing illness. But for those with weaker immune systems, such as older people, pregnant women and those with immune system disorders, the parasite can cause toxoplasmosis.

Toxoplasmosis a disease characterized by flu-like symptoms, including swollen lymph glands and muscle aches and pains. In severe cases, toxoplasmosis can cause damage to the eyes, brain and other organs.

Some studies, however, have linked T. gondii infection to mental health conditions. In 2012, for example, Medical News Today reported on a study linking T. gondi to increased risk of self-harm or suicide among new mothers.

More recently, studies have linked T. gondii infection to schizophrenia, and some have found that antipsychotic medication may even stop the parasite from replicating. But such research has been met with much criticism.

In this latest study, Gary Smith, of the School of Veterinary Medicine at the University of Pennsylvania, wanted to gain a better understanding of the link between T. gondii infection and schizophrenia.

Link between T. gondii and schizophrenia ‘should be considered, not ridiculed’

Smith wanted to determine the proportion of schizophrenia cases that could be attributable to T.gondii infection. He did this by calculating the population attributable fraction (PAF) – a measure used by epidemiologists to understand the importance of a risk factor.

“In other words,” explains Smith, “we ask, if you could stop infections with this parasite, how many [schizophrenia] cases could you prevent?”

Smith calculated the PAF fraction throughout an average lifetime to be 21.4%, meaning that a fifth of all schizophrenia cases over a lifetime could be prevented by stopping T. gondiiinfections from occurring. “That, to me, is significant,” says Smith.

He notes that many countries have a much higher prevalence of T. gondii infections than the US, and such countries also have a higher prevalence of schizophrenia.

Schizophrenia is one of the leading causes of disability in the US, affecting more than 3.5 million people.

Smith believes that his findings indicate the importance of gaining a better understanding of the link between T. gondii infection and schizophrenia. He adds:

By finding out how important a factor T. gondii infection is, this work might inform our attitude to researching the subject.

Instead of ridiculing the idea of a connection between T. gondiiand schizophrenia because it seems so extraordinary, we can sit down and consider the evidence. Perhaps then we might be persuaded to look for more ways to reduce the number of people infected with toxoplasma.”

Common food preservative may help to treat schizophrenia

A new randomized trial from Taiwan shows that a common food preservative could enhance the effect of a schizophrenia drug, even in the case of people normally resistant to treatment.
older man taking pillsNew research suggests that a common food preservative could be the answer for treatment-resistant people with schizophrenia.

Schizophrenia is a chronic, sometimes disabling mental disorder characterized by delusions, flat affect, agitated movements, and a difficulty in sustaining activities.

Treatments include antipsychotic medication — such as brexpiprazole, clozapine, or risperidone — and psychosocial treatments.

Studies have shown that “one fifth to one half of [people with schizophrenia] are classified as refractory to pharmacological treatment,” meaning that they do not respond to antipsychotics.

Researchers from China Medical University in Taiwan may now have found a way of boosting the effectiveness of certain drugs, which may help some people living with schizophrenia to respond better to treatment.

The answer, says the study’s lead investigator Dr. Hsien-Yuan Lane, may be found in a common food preservative: sodium benzoate. Dr. Lane and team conducted a randomized, double-blind, placebo-controlled trial showing that this preservative could enhance the effects of the antipsychotic drug clozapine.

“Clozapine,” he explains, “is considered the last-line antipsychotic agent for patients with refractory schizophrenia.” Despite this, a significant number of people living with schizophrenia are resistant to this drug.

The new trial seems to confirm for the first time that sodium benzoate — which has successfully been used as an add-on to other antipsychotics — can be added to clozapine to improve the symptoms of drug-resistant patients.

Dr. Lane and colleagues’ findings were recently published in the journal Biological Psychiatry. “If the finding can be confirmed, this approach may bring hope for treating patients with the most refractory schizophrenia,” he suggests.

Sodium Benzoate, a D-Amino Acid Oxidase Inhibitor, Added to Clozapine for the Treatment of Schizophrenia_ A Randomized, Double-Blind, Placebo-Controlled Trial

D-Amino Acid Oxidase Inhibition A New Glutamate Twist for Clozapine Augmentation in Schizophrenia

A series of clinical trials
found that currently available NMDA-enhancing agents
including glycine, D-cycloserine, D-serine, and sarcosine were
efficacious in improving the overall psychopathology of
schizophrenia without side effect or safety concern.

16. Lin CH, Lane HY, Tsai GE (2012): Glutamate signaling in the pathophysiology and therapy of schizophrenia. Pharmacol Biochem Behav 100:665–677.
17. Heresco-Levy U (2005): Glutamatergic neurotransmission modulators as emerging new drugs for schizophrenia. Expert Opin Emerg Drugs 10:827–844.
18. Coyle JT (2012): NMDA receptor and schizophrenia: A brief history. Schizophr Bull 38:920–926.
19. Javitt DC, Schoepp D, Kalivas PW, Volkow ND, Zarate C, Merchant K, et al. (2011): Translating glutamate: From pathophysiology to treatment.Sci Transl Med 3:102mr102.

Cat ownership in childhood linked to greater risk of later-life mental illness

They are cute, fluffy and have that wide-eyed glare that few of us can resist; it is no wonder more than 95 million of us own a cat. But there may be a darker side to our four-legged friends. New research claims the animals could increase our risk of mental illnesses, including schizophrenia and bipolar disorder.
Cat using litter boxHumans can become infected with Toxoplasma gondii by accidentally swallowing the parasite after coming into contact with a cat’s feces.

Two studies published in the journals Schizophrenia Research and Acta Psychiatrica Scandinavica attribute this association to Toxoplasma gondii – a parasite found in the intestines of cats. Humans can become infected with the parasite by accidentally swallowing it after coming into contact with the animal’s feces.

T. gondii is the cause of a disease known as toxoplasmosis. According to the Centers for Disease Control and Prevention (CDC), more than 60 million people in the US are infected with the parasite, though the majority of people are not aware of it.

People with a healthy immune system often stave off T. gondii infection, so it does not present any symptoms. However, pregnant women and people with weakened immune systems are more susceptible to infection and may experience flu-like symptoms – such as muscle aches and pains and swollen lymph nodes – as a result, while more severe infection may cause blindness and even death.

Previous studies have also linked T. gondii infection to greater risk of mental disorders. In November 2014, for example, Medical News Today reported on a study claiming the parasite is responsible for around a fifth of schizophrenia cases. Now, new research provides further evidence of this association.

Link between T. gondii and schizophrenia ‘should be considered, not ridiculed’

Smith wanted to determine the proportion of schizophrenia cases that could be attributable to T.gondii infection. He did this by calculating the population attributable fraction (PAF) – a measure used by epidemiologists to understand the importance of a risk factor.

“In other words,” explains Smith, “we ask, if you could stop infections with this parasite, how many [schizophrenia] cases could you prevent?”

Smith calculated the PAF fraction throughout an average lifetime to be 21.4%, meaning that a fifth of all schizophrenia cases over a lifetime could be prevented by stopping T. gondiiinfections from occurring. “That, to me, is significant,” says Smith.

He notes that many countries have a much higher prevalence of T. gondii infections than the US, and such countries also have a higher prevalence of schizophrenia.

Schizophrenia is one of the leading causes of disability in the US, affecting more than 3.5 million people.

Smith believes that his findings indicate the importance of gaining a better understanding of the link between T. gondii infection and schizophrenia. He adds:

By finding out how important a factor T. gondii infection is, this work might inform our attitude to researching the subject.

Instead of ridiculing the idea of a connection between T. gondiiand schizophrenia because it seems so extraordinary, we can sit down and consider the evidence. Perhaps then we might be persuaded to look for more ways to reduce the number of people infected with toxoplasma.”

People with ‘rage’ disorder twice as likely to have toxoplasmosis

A disorder that causes the individual to fly off the handle unexpectedly, as in road rage, has been significantly linked with toxoplasmosis, a parasite commonly associated with cat feces, according to the Journal of Clinical Psychiatry.

[road rage]

People with IED are prone to sudden anger.

Intermittent explosive disorder (IED) has been defined as “recurrent, impulsive, problematic outbursts of verbal or physical aggression that are disproportionate to the situations that trigger them.”

Up to 16 million Americans are thought to have IED, more than the total number for bipolar disorder and schizophrenia combined.

Toxoplasmosis is a common and generally harmless parasitic infection that is passed on through the feces of infected cats, contaminated water or undercooked meat.

 

It affects around 30% of all humans but is normally latent1.

Research has revealed that the parasite is found in brain tissue, and it has been linked to a number of psychiatric conditions, including schizophrenia, bipolar disorder and suicidal behavior.

Researchers from the University of Chicago, led by Dr. Emil Coccaro, have been looking for more effective ways to diagnose and treat IED and impulsive aggression.

 

This is a scanning electron micrograph of the protozoan parasite Toxoplasma gondii, tissue cyst in brain of an infected mouse.
Credit: David Ferguson

Individuals with a psychiatric disorder involving recurrent bouts of extreme, impulsive anger–road rage, for example–are more than twice as likely to have been exposed to a common parasite than healthy individuals with no psychiatric diagnosis.

In a study involving 358 adult subjects, a team led by researchers from the University of Chicago found that toxoplasmosis, a relatively harmless parasitic infection carried by an estimated 30 percent of all humans, is associated with intermittent explosive disorder and increased aggression.

The findings are published in the Journal of Clinical Psychiatry on March 23, 2016.

“Our work suggests that latent infection with the toxoplasma gondiiparasite may change brain chemistry in a fashion that increases the risk of aggressive behavior,” said senior study author Emil Coccaro, MD, Ellen. C. Manning Professor and Chair of Psychiatry and Behavioral Neuroscience at the University of Chicago.

“However, we do not know if this relationship is causal, and not everyone that tests positive for toxoplasmosis will have aggression issues,” Coccaro said, adding that additional studies are needed.

Intermittent explosive disorder (IED) is defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, as recurrent, impulsive, problematic outbursts of verbal or physical aggression that are disproportionate to the situations that trigger them. IED is thought to affect as many as 16 million Americans, more than bipolar disorder and schizophrenia combined.

As part of their pioneering research to improve diagnosis and treatment for IED and impulsive aggression, Coccaro and his colleagues examined possible connections to toxoplasmosis, an extremely common parasitic infection. Transmitted through the feces of infected cats, undercooked meat or contaminated water, toxoplasmosis is typically latent and harmless for healthy adults. However, it is known to reside in brain tissue, and has been linked to several psychiatric diseases, including schizophrenia, bipolar disorder and suicidal behavior.

The research team recruited 358 adult subjects from the U.S., who were evaluated for IED, personality disorder, depression and other psychiatric disorders. Study participants were also scored on traits including anger, aggression and impulsivity. Participants fell into one of three groups. Roughly one third had IED. One third were healthy controls with no psychiatric history. The remaining third were individuals diagnosed with some psychiatric disorder, but not IED. This last group served as a control to distinguish IED from possible confounding psychiatric factors.

Hold your cats

The research team found that IED-diagnosed group was more than twice as likely to test positive for toxoplasmosis exposure (22 percent) as measured by a blood test, compared to the healthy control group (9 percent).

Around 16 percent of the psychiatric control group tested positive for toxoplasmosis, but had similar aggression and impulsivity scores to the healthy control group. IED-diagnosed subjects scored much higher on both measures than either control group.

Across all study subjects, toxoplasmosis-positive individuals scored significantly higher on scores of anger and aggression. The team noted a link between toxoplasmosis and increased impulsivity, but when adjusted for aggression scores, this link became non-significant. This finding suggests toxoplasmosis and aggression are most strongly correlated.

However, the authors caution that the study results do not address whether toxoplasmosis infection may cause increased aggression or IED.

“Correlation is not causation, and this is definitely not a sign that people should get rid of their cats,” said study co-author Royce Lee, MD, Associate Professor of Psychiatry and Behavioral Neuroscience at the University of Chicago. “We don’t yet understand the mechanisms involved–it could be an increased inflammatory response, direct brain modulation by the parasite, or even reverse causation where aggressive individuals tend to have more cats or eat more undercooked meat. Our study signals the need for more research and more evidence in humans.”

Coccaro and his team are now further examining the relationship between toxoplasmosis, aggression and IED. If better understood, this connection may inform new strategies to diagnose or treat IED in the future.

“It will take experimental studies to see if treating a latent toxoplasmosis infection with medication reduces aggressiveness,” Coccaro said. “If we can learn more, it could provide rational to treat IED in toxoplasmosis-positive patients by first treating the latent infection.”

People with rage disorder twice as likely to have latent toxoplasmosis parasite infection

Adjunctive Use of a Standardized Extract of Withania somnifera (Ashwagandha) to Treat Symptom Exacerbation in Schizophrenia

22% of subjects with IED tested positive for the parasite

In the current study, the authors evaluated 358 adult Americans for IED, personality disorderdepression and other psychiatric disorders and gave them scores for traits such as anger, aggression and impulsivity. They also screened for toxoplasmosis using blood tests.

Fast facts about toxoplasmosis

  • Around 60 million Americans are thought to have toxoplasmosis
  • If a woman catches it just before or during pregnancy, it can be dangerous for the baby
  • For those with a weakened immune system, there are medications to treat it.

They then classified the participants into three groups: approximately one third had IED, one third were healthy controls with no psychiatric history, and one third had received a diagnosis for a psychiatric disorder but not IED.

The purpose of the last group was to enable the team to distinguish IED from other psychiatric factors.

Findings showed that 22% of those with IED tested positive for toxoplasmosis exposure, compared with 9% of the healthy control group and 16% of the psychiatric control group.

The psychiatric group and the healthy group had similar scores for aggression and impulsivity, but the group with IED scored far higher on both counts than either of the other two groups.

An association emerged between toxoplasmosis and impulsivity. However, when the team adjusted for aggression scores, this association became non-significant, indicating a strong correlation between toxoplasmosis and aggression.

The authors point out that the findings do not mean that toxoplasmosis causes IED, or that people with cats are more likely to have the condition. It simply reveals a relationship.

T. gondii infection ‘may double schizophrenia risk’

For one study, Dr. Robert H. Yolken, of the Stanley Laboratory of Developmental Neurovirology at Johns Hopkins University School of Medicine in Baltimore, MD, and colleagues assessed the results of two previous studies.

These studies had identified a link between cat ownership in childhood and development of later-life schizophrenia and other mental disorders, comparing them with the results of a 1982 National Alliance for the Mentally Ill (NAMI) questionnaire.

The NAMI questionnaire – conducted around a decade before any data was published on cat ownership and mental illness – revealed that around 50% of individuals who had a cat as a family pet during childhood were diagnosed with schizophrenia or other mental illnesses later in life, compared with 42% who did not have a cat during childhood.

The questionnaire, the researchers say, produced similar results to those of the two previous studies, suggesting that “cat ownership in childhood is significantly more common in families in which the child later becomes seriously mentally ill.”

“If true,” the authors add, “an explanatory mechanism may be T. gondii. We urge our colleagues to try and replicate these findings to clarify whether childhood cat ownership is truly a risk factor for later schizophrenia.”

In another study, A. L. Sutterland, of the Academic Medical Centre in Amsterdam, the Netherlands, and colleagues conducted a meta-analysis of more than 50 studies that established a link between T. gondii and increased risk of schizophrenia.

They found that people infected with T. gondii are at more than double the risk of developing schizophrenia than those not infected with the parasite.

The team also identified a link between T. gondii infection and greater risk of bipolar disorderobsessive-compulsive disorder (OCD) and addiction.

“These findings suggest that T. gondii infection is associated with several psychiatric disorders and that in schizophrenia, reactivation of latent T. gondii infection may occur,” note the authors.

The CDC recommend changing a cat’s litter box every day to reduce the risk of T. gondii infection, noting that the parasite does not become infectious until 1-5 days after it has been shed in the animal’s feces.

They also recommend feeding cats only canned or dried commercial foods or well-cooked meats; feeding them raw or undercooked meats can increase the presence of T. gondii in a cat’s feces.

It is important to note that cat feces are not the only source of T. gondii infection. Humans can contract the parasite through consuming undercooked or contaminated meats and by drinking contaminated water.

How a cat parasite can change your personality

A new study suggests that infection with the cat-borne parasite Toxoplasma gondii could make people more risk-prone and likely to start their own business.
cute kitten

Your cute cat may host a parasite that could influence your behavior in surprising ways.

As humans who still inherit Enlightenment’s worship of rationality, we like to think that our decisions are autonomous and driven by reason alone.

However, science seems to contradict this popular belief. More and more research is showing that microorganisms such as bacteria and viruses influence our behavior and emotional states.

For instance, the bacteria in our guts may be responsible for states of anxiety and depression. Conversely, other studies have shown that some probiotic bacteria may relieve the effects of stress.

Now, a new study suggests that infection with the cat-borne parasite Toxoplasma gondii could make people change their behavior so that they become more prone to business and entrepreneurial ventures.

Stefanie K. Johnson, an associate professor at the University of Colorado (CU) Boulder’s Leeds School of Business, co-led the research in collaboration with Pieter Johnson, a professor in CU Boulder’s Department of Ecology and Evolutionary Biology.

The findings were published in the journal Proceedings of the Royal Society B.