Kindling: Is the theory that each episode of mental illness makes another more likely true?

The concept was first used in regards to epilepsy but has since been used to explain mood disorders

10 October is World Mental Health Day (iStock )

It’s a fact that mental illness can debilitate a person’s life just as acutely as physical conditions. What is less understood, however, is what exactly causes a person to suffer from conditions like depression, anxiety, or bipolar.

The kindling hypothesis is just one explanation that experts consider when trying to understand how and why mental illness affects us. Kindling is a term used to describe how some people slip down into the psychological rabbit hole of a mental health crisis in shorter periods of time and with less extreme triggers. When once a person would be thrust into a depressive episode by a major life event, such as a bereavement, less earth-shattering events like a squabble at work seem to set people off with ever more extreme symptoms - like a pane of glass that is more susceptible to breaking once it is cracked, or the foundations of a fire burning more fiercely with every twig thrown onto it.

But kindling is a controversial concept. Its logical conclusion seems to be a state where sufferers must put up with having their lives interrupted by illness more frequently and in unavoidable ways. It suggests that episodes of mental illness damage us on a neurological level that can't be overcome. So what is the truth?

Kindling was a term coined in the 1960s in relation to epilepsy, when US scientists found that the severity of electrically induced seizures in cats and rats worsened each time they were administered and were set off more easily. The parts of the brain which caused seizures appeared to be primed for another attack with each instance. This is linked to a phenomenon known as neuroplasticity, where the brain learns responses to certain triggers.

In the 1980s, psychiatrist Robert Post at George Washington University applied the term to explain a pattern he had noticed in patients with mood disorders: that low periods were kicked off easier and in shorter spaces of time. He wondered, was the brain priming pathways for triggering conditions like clinical depression, bipolar and PTSD in the same way it was epilepsy?

“The kindling model helps us think about the progression, the unfolding and evolution of the illness,” he commented in a The New York Times piece in 1988. He devoted further research into explaining how psychotherapy and medications could be used to prevent this kindling effect. Later research has indicated that each bout of a mood disorders damage brain cells and nerve pathways and making a person susceptible to attacks, and turning the hormonal response to stress out of whack.

So, where does that leave the average sufferer when most of us will experience mental illness at some point in our lives? Are we really doomed to a worsening spiral of ill-health?

The resounding answer from experts is “no”. Kindling is just one hypothesis used to explain why some people’s mental health appears to worsen, and is not a universal eventuality by any means. Mental health is nowhere near that fatalistic or, frankly, easy to pin down.

Firstly, mental illness isn’t merely set off by pathological abnormalities in the body, but is a normal response to the stresses of life. For the minority of people who do experience kindling, medication can be used to prevent and treat its debilitating effects.

“It’s a slightly odd theory,” says Peter Kinderman, professor of clinical psychology at the University of Liverpool. “There are about 65million other things that are more important when it comes to a person’s mental health,” he says.

If anything, most people tend to learn to cope with mental illness better as they grow older, as they become more settled and can notice what might set them off. In addition, life tends to become more stressful. Kinderman uses the analogy of a group of people being by acid and some going blind: no one would try to find fault with the person’s body for having been injured.

“There is a struggle for coming up with analogies from the world of biological medicine to apply to the world of mental health which stretch those analogies a long way. And this is one of them,” he says.

“What I'm interested in more is the idea that what is important that the emotions are part of human life and not studied through a microscope,” he says.

“Plucking a biomedical explanation and using it for mental health is worrying because it implies we can think of mental health problems like any other. It doesn't work that way. “

“What is much more interesting is the sociological story about why people look for biomedical explanation for misery.”

Prevention, stresses Dr Brian Marien of the Positive Group, which helps schools and workplaces with mental illness, is more important than worrying about kindling. He says that while neuroplasticity is undeniable, this is one small factor that plays into a person’s mental health.

Rather than worrying about kindling and psychological jargon, we should educate young people to identify, understand and cope with triggers to avoid developing chronic mental illnesses altogether.

“For some - the more often they get depressed - the more easily the next episode is triggered - due to kindling and sensitisation. We need to have good reactive services to help reduce the severity and duration of anxiety and depression in the first place.

“Humans aren't happy all the time and we can feel sad and happy and distressed and a lot of the distress and unhappiness in adulthood has its genesis during our formative years.”

“This is an area of psychology called metacognition. If you or I became anxious or depressed what happens is that if I get anxious I think ‘oh my god, I’m losing control, it’s going to stop me fulfilling my potential’. I might become anxious about feeling anxious, and that makes me more anxious and there’s a danger that triggers a kindling process or a neural sensitisation.”

He stresses that there is always hope for people with mental illness. "The aim is prevention and early intervention because the research shows that medication can reduce relapse of depression, cognitive behavioural therapyis an effective treatment for anxiety and can reduce the risk of relapse of depression; mindfulness based cognitive therapy (MBCT) can reduce depressive relapse and early intervention is protective and would reduce the kindling and or sensitisation process," he explains, adding: "Prevention is better than cure.”