Is there really a link between owning a cat and mental illness?

Over the past few years, cats have increasingly attracted media attention due to a number of scientific studies reporting that a Toxoplasma Gondii (T. Gondii) infection is linked with mental health issues, including schizophrenia, suicide and intermittent rage disorder. Since domestic cats are the primary hosts of T. Gondii – that is, they provide an environment within which this parasite can reproduce – it is often speculated that cat ownership may put people at increased risk of mental illness, by exposing them to it.

However, only a handful of small studies have found evidence to support a link between owning a cat and psychotic disorders, such as schizophrenia. And most of these investigations have serious limitations. For instance, they relied on small samples, did not specify how participants were selected, and did not appropriately account for the presence of missing data and alternative explanations. This can often lead to results that are born out of chance or are biased.

To tackle these limitations, we conducted a study using data from approximately 5,000 children who took part in the Avon Longitudinal Study of Parents and Children between 1991 and 1992. Since then, these children and their families have been followed up to gather information on their health, as well as on their demographic, social and economic circumstances.

So, unlike previous studies, we were able to follow people over time, from birth to late adolescence, and address a number of the limitations of previous research, including controlling for alternative explanations (such as income, occupation, ethnicity, other pet ownership and over-crowding) and taking into account missing data.

T. Gondii is found in domestic cats. Kateryna Kon/Shutterstock.com

We studied whether mothers who owned a cat while pregnant; when the child was four years old; and 10 years old, were more likely to have children who reported psychotic symptoms, such as paranoia or hallucinations, at age 13 and 18 years of age. Although most people who experience psychotic symptoms in adolescence will not develop psychotic disorders later in life, these symptoms often indicate an increased risk for such disorders and other mental illnesses, including depression.
So are cats bad for your mental health? Probably, not.

We found that children who were born and raised in households that included cats at any time period – that is, pregnancy, early and late childhood – were not at a higher risk of having psychotic symptoms when they were 13 or 18 years old. This finding in a large, representative sample did not change when we used statistical techniques to account for missing data and alternative explanations. This means that it is unlikely that our results are explained by chance or are biased.

While this finding is reassuring, there is evidence linking exposure to T. Gondii in pregnancy to a risk of miscarriage and stillbirth, or health problems in the baby. In our study, we could not directly measure exposure to T. Gondii, so we recommend that pregnant women should continue to avoid handling soiled cat litter and other sources of T. Gondii infection, such as raw or undercooked meats, or unwashed fruit and vegetables. That said, data from our study suggests that owning a cat during pregnancy or in early childhood does not pose a direct risk for offspring having psychotic symptoms later in life.

Francesca Solmi, Research Associate, UCL and James Kirkbride, Reader, UCL
This article was originally published on The Conversation.

Calming our minds is the first step

Teaching given at Bodhi Path Washington, DC Metro Area in Spring 2004.

Today, I will give you instructions about mind nature that will be helpful for your meditation. And, I will give you reasons for doing the shamatha or calm-abiding meditation practice. To meditate, you first need some understanding about your mind. Our normal concepts about mind, which really are not accurate, can disturb your meditation. Therefore, it is very important to have a correct understanding about the nature of mind.

 Generally, people today view mind from a scientific perspective. Perhaps they equate mind, which is a process, with the brain, which is a bodily organ. In this case, it is easy to see mind as no more than a collection of nerves transmitting and processing electronic signals, like a computer made of flesh. I should tell you that if mind functioned in this way, then there would be no need to meditate. In fact, you could not meditate at all with such a mind. However, for Buddhists, mind is not like this. In Buddhist terms, we say that mind is clear. Clarity here means mind can understand itself. We can understand things because the mind’s true nature is self-understanding. Otherwise, we could not learn anything. To learn in the Buddhist sense means to gain self-understanding.

All conceptual knowledge comes to us as pictures in our minds. The physical objects that we comprehend are not themselves of the same material as our minds. Physical objects have atoms, while minds do not. This makes physical objects different than mind.

Mind itself is not made of atoms. Thus, mind has its own, separate nature from physical objects. If we reason this out, it means that in reality, there is no contact between mind and matter. When you understand that objects are just reflections in the mind, then you realize that what your mind comprehends are not objects themselves, but merely images or pictures. Through this concept of mind you can then approach the more difficult idea that mind-nature is defined by self understanding and self-realization. Every moment mind is working, it is moving. Mind is not a fixed thing with some permanence, but a process; a true mind-stream. So, as thoughts pass through mind, they themselves ensure mind’s continuance. If mind were to remain always on one thought, then it would get stuck. It would be frozen. But because mind is always moving, because it is dynamic, then you can perceive the outside world through ever-changing sense data. You can see, hear and feel. For example, we might compare the mind-stream to reading a series of words quickly. Each word is connected to a thought. The only way you can comprehend a series of thoughts is because your mind is not a fixed, unchanging entity. If your mind was not dynamic, then it would get stuck on "A," and never able to get to "B." So, in every moment, the mind is moving; it is passing by its former position. When we are fully awake, mind is free of the object with which it connects to through thoughts, perceptions and feelings. Mind is unobstructed. You neither have a single thought nor many thoughts. Mind does not exist substantially. Mind is no longer ignorant or stupid in the deepest sense.
But we should understand that self-realization is not like being in a coma. Instead, there is clarity and power. Self-realized mind is free from the influence of phenomena. It is mind free from all need to occupy itself; it is now an independent mind.

This, we might say, is good mind, non-dualistic mind. Of course, this kind of mind is not easy to obtain. Our habits are strong, and the unrealized mind is easily carried away by the flow of thoughts. If you examine your own mind, you will understand this. Mind does not exist in tangible substance; it is not a physically existing thing. Mind is not limited by any size, any shape, or any color. It is boundless and spacious. When you can realize an open state of mind—and keep it stable—then you can develop this state without limit. You can call this state enlightened mind, but enlightenment is difficult to realize. You may be able to realize this state of mind through examination or analysis. But your mind won’t stay in this state for long. It quickly disappears because of your mental habits. I’m talking primarily about the mental habit of confusion and agitation. This habit of agitation is very, very strong. Our minds and those of all living beings are nothing if not restless. While the basic nature of our mind is clear and limitless, our present mind is restless because agitation is a mental habit. Therefore, meditation is the natural antidote. Systematically organized meditation techniques are available to solve this problem of mental agitation. In other words, we have to train our minds.

Right now, our minds are wild and agitated, like a confused hurricane. To realize our full potential, we must tame our minds. And the good news is that we can use the mind to tame itself. We need to develop new mental habits. Among the many varieties of methods used to tame the mind, one of the most powerful is taught at Bodhi Path Centers—the practice of shamatha meditation. You should concentrate on practicing shamatha a great deal.

 By Shamar Rinpoche

Health Check: what are 'coffee naps' and can they help you power through the day?

Caffeine and napping have something in common. Both make you feel alert and can enhance your performance, whether that’s driving, working or studying. But some people are convinced that drinking a coffee before a nap gives you an extra zap of energy when you wake up.


How could that be? Is there any evidence to back the power of these so-called coffee naps? Or are we better off getting a good night’s sleep?

Feeling sleepy?

If you don’t get enough sleep, you incur what researchers call a sleep debt. You can build up a sleep debt without realising it, on purpose or when you feel you have no other option, like to meet work or other deadlines.

Taking a nap is a common way of overcoming your sleepiness and repaying your sleep debt. Drinking coffee can also help us get through the day. And since the 1990s, researchers have been studying how combining the two might help.

In a 1997 study, 12 sleep-deprived people drank the equivalent of one large cup of brewed coffee and five minutes later had the chance to nap for 15 minutes. They then did some driving tests in a simulator to check their alertness.

Although drinking a coffee (without a nap) helped their driving performance, combining caffeine with a nap (a coffee nap) improved it even further. People who took a coffee nap were less likely to drift out of their lanes on a two hour monotonous simulated drive, compared to when they just drank a coffee (and had no nap) or when they had a decaffeinated coffee (and without a nap).

A coffee nap even helped performance if people dozed during their nap time rather than falling into a deeper sleep. A coffee nap also reduced sleepiness once people got up, with people remaining alert for a couple of hours.

However, this early, small study raised many questions. For instance, we don’t know how much coffee the people in the study were used to drinking or if they were what researchers call caffeine-naive and so more likely to experience a greater caffeine “hit”.

How might coffee naps work?

To understand how a coffee nap might work, we need to look at how the body processes caffeine. When you drink a coffee, the caffeine stays in the stomach for a while before moving to the small intestine. It is from here that caffeine is absorbed and distributed throughout the body. This process, from drinking to absorption, takes 45 minutes.

But caffeine’s alerting effect kicks in sooner, about 30 minutes after drinking. So, drinking a coffee just before a short nap of less than 15 minutes doesn’t affect the nap as your body hasn’t yet experienced the caffeine hit.

Once you wake up from your nap, not only do you experience the hit, your body feels the effects of the caffeine hours later. Although caffeine is broken down in the liver, half of it remains in the blood for 4-5 hours after drinking a moderate amount (equivalent to two large cups of brewed coffee). It takes more time to eliminate greater amounts of caffeine from the body.

It is this caffeine hit after you wake up and the “long tail” of caffeine in your body that helps you power through the day.

How caffeine naps help you stay alert.

But if you mis-time your nap, for instance taking it after the caffeine hit and not before, this will mess up your sleep and your performance. This can happen if you wait too long after drinking your coffee before taking your nap.

How much coffee is safe?

While there’s evidence that coffee naps work, are they safe?
If we consider caffeine consumption, doses of 300-500mg a day (equivalent to 2-3 large cups of brewed coffee) seem safe, as about 70% of caffeine is converted into paraxanthine, which has no apparent toxic effects.
But drinking too much caffeine (more than 500mg a day) can produce symptoms of nervousness, anxiety, irritability, and body effects of restlessness, palpitation, agitation, chills, tremors and increased urine flow.

Food Standards Australia New Zealand says 95mg of caffeine a day (about two cans of cola) in children aged 5-12, and 210mg a day (about three cups of instant coffee) in adults increase anxiety levels.

It’s easy to consume more caffeine than we need. Drinks containing caffeine are on our supermarket shelves (such as Red Bull and V energy drinks) and in over-the-counter medicines (such as Panadol Extra). You can keep an eye on your caffeine intake by checking the caffeine content of common drinks, foods and medicines.

If you are drinking too much caffeine and want to stop, withdrawal can cause headache, sleepiness and decreased alertness. So, given the addictive properties of caffeine, “caffeine use disorder” has been classified as “a condition for further study” in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).

Are coffee naps the best way to pay back sleep debt?

While coffee naps will power you for a couple of hours, they’re not the best way to pay back your sleep debt.

Getting enough sleep on most days is a better solution for alertness, performance and productivity. That’s because sleeping is vital for a range of brain and body functions.

Getting enough sleep also reduces your risk of a car accident, weight gain, obesity, diabetes and depression.
Chin Moi Chow, Associate Professor of Sleep and Wellbeing, University of Sydney
This article was originally published on The Conversation.

Fructose: friend or foe?

Fructose has been getting a bad rap lately. Although consuming too much can be bad for your health, those who exercise seem to be protected against some of fructose’s negative health effects. And growing evidence suggests that fructose can help athletes recover after exercise.


Fructose and glucose are the two carbohydrates that make up table sugar. Although fructose has largely been blamed for many of the negative health effects of sugar, it has some useful roles in the body.

Most of the glucose we consume ends up in our muscles where it is either stored in a form called glycogen or burned as a fuel. But fructose is mainly metabolised by the liver because muscle cannot easily use fructose as a fuel, and this special metabolism is thought to lead to some of its negative health effects.

The liver converts fructose into other useful substances, such as carbohydrates (glucose or lactate) or fat, which are then delivered to various parts of the body via the bloodstream, to be used as fuel. But if more glucose and fats enter the bloodstream than are removed by muscles and other tissues, it can lead to a build up in the bloodstream.

High levels of blood glucose and fats are associated with an increased risk of heart disease, stroke and type 2 diabetes. But the increase in blood-fat levels, seen with high fructose intake, is still considered to be within the normal range. Whether the small rises in blood fats with high fructose intake can truly result in an increased risk of disease is not yet certain.

An increase in blood-fat levels also depends on how physically active you are. If you exercise every day, consuming huge amounts of fructose – comparable to 50 teaspoons of table sugar or more than five cans of soft drink per day – does not seem to influence blood-fat levels. So, if you have a sweet tooth, exercise is advisable.

For athletes, fructose may even play a beneficial role in the diet. Athletes who perform in endurance sports, such as marathons, triathlons and cycling, may have multiple training sessions each day. This means that they often need to be at their physical best on more than one occasion within a 24-hour period. The main factor limiting these athletes is their bodily stores of carbohydrates as glycogen.

Opening ‘doors’

Glycogen is a molecule that is stored in the muscles and is vital for performing intense exercise since it can be quickly broken down into glucose and used as fuel. The liver also stores glycogen which serves as a critical source of glucose to stabilise blood-sugar levels when they become low.
When athletes train heavily or compete, it is important they replace any used glycogen stores between bouts of exercise to enable optimal performance in later events. They also need to get a lot of carbohydrate, in the form of glucose and fructose, into their bloodstream quickly during and after exercise, so that their liver and muscles can use it as fuel.

Fructose-glucose mixtures are best for athletes. pixelrain/Shutterstock

The main route for glucose absorption from the gut is through a transporter called SGLT1 - a protein that acts like a door, helping glucose go from the gut to the bloodstream. SGLT1 is thought to have a maximum capacity for glucose transport because it can only transport around one gram of glucose per minute. Fructose, however, can be transported into the bloodstream using a different “door”, called GLUT5. By using both routes, rather than just SGLT1, athletes can increase the amount of ingested carbohydrate the body can use during exercise.

The rapid absorption of fructose-glucose mixtures and special handling of fructose in the liver are the two main reasons that fructose can also help to speed up recovery after exercise. We recently found that when cyclists drank sports drinks containing both fructose and glucose after exercise, they accelerated the recovery of their liver glycogen stores. It almost doubled this rate of recovery compared with glucose-only drinks, when the same total amount of carbohydrate was consumed.
Athletes often need to consume lots of carbohydrate to fuel their exercise. The amount of carbohydrate they can consume during a race is almost never enough to prevent their stores of glycogen from depleting. This is because the ability of the gut to digest and absorb the carbohydrate is limited.

The muscles can use this glucose quicker than we can digest and absorb carbohydrates. As a result, the gut is pushed to its maximum capacity and athletes can suffer from stomach problems, such as bloating. One of the noticeable advantages for athletes is that when they consume fructose-glucose mixtures in sports drinks and gels they experience fewer stomach problems compared with glucose-only sports drinks. The rapid transport of fructose means less sugar is left in the stomach and intestine during exercise, which is usually the main cause of stomach complaints.

So, although fructose may have its downfalls, these are possibly only a problem for people who are inactive. Even modest amounts of exercise may be enough to prevent some of the negative health effects. For the endurance athlete, not only is fructose unlikely to cause harm, there are even some useful effects for athletic performance.

Javier Gonzalez, Lecturer (Assistant Professor), University of Bath
This article was originally published on The Conversation.