We may live in a throwaway society but up to two million people in the UK are compulsive hoarders.
According to new research, it first becomes a problem in 30-somethings, and affects more people with age, with seven per cent of the over-70s affected.
Hoarding is not just about holding on to your children's school paintings, but is defined as the excessive collection of items that often appear to have no value, coupled with an inability to get rid of them.
According to the NHS, those affected acquire an excessive number of items and store them in a chaotic manner, and it's considered to be a problem if the clutter interferes with everyday living and causes significant distress or affects quality of life.
But it is a problem that responds to treatment: hoarding was once thought to be a form of obsessive compulsive disorder (OCD), however, OCD treatments have been largely ineffective.
Hoarding is now regarded as a standalone condition with treatments specific to it research shows these can help in up to 70% of cases.
Many hoarders collect anything, while others focus on certain items: clothes, newspapers and books are the most common items, according to a study published by Michigan University, but the list also includes things such as till receipts, empty cans, rubbish and grass cuttings.
Hoarding is poorly understood,' says Dr Cosmo Hallstrom, a consultant psychiatrist in private practice in London, and a spokesman for the Royal College of Psychiatrists.
There is a little bit of it in all of us. We get attached to things and we do not want to throw them away, that is part of human behaviour. But in some it gets out of hand, and becomes a problem.
Hoarding often starts in a small way, and it seems that the judgment of hoarders is impaired in some way. They often, for example, over-value the possessions they have collected.
Whatever hoarders see in terms of clutter doesn't seem to matter to them. What matters is the fact that these things have importance to them and losing them would trigger distress.'
The most frequent reason given for holding on to things is to prevent waste, although emotional attachments and superstitions are also important. A common belief is that if something is thrown away, something bad will happen.
The Michigan research shows that people who hoard tend to form intense emotional attachments to a wider variety of objects than normal.
They often attach human-like qualities to inanimate objects, feeling grief at the prospect of getting rid of them, and believe they are safer when they are surrounded by them.
One theory is that hoarding is some kind of evolutionary trait, and the need to survive has given us all a propensity to squirrel away useful things, such as food and fuel, but in people with hoarding disorder, the normal checks and balances have gone awry.
The increasing prevalence with age may be linked to mental decline and a difficulty in decision-making brain scans and other studies have shown that hoarding seems to involve abnormalities in areas of the brain involved in decision-making, attention, organisation, and the regulation of emotions.
Depression and anxiety are common co-symptoms, and there is frequently a family history of hoarding. For many years, it was thought that just a tiny proportion of the population, about 0.4 per cent, was affected, but that figure was largely based on hoarding as a symptom of OCD.
In 2013 it was classed as a separate condition, and the latest research, based on more than 15,000 twins aged 15 to 97, suggests it's five times more common, affecting more than two per cent of adults.
The research, reported in the American Journal of Geriatric Psychiatry, also revealed that more of us are affected as we get older.
The prevalence and severity of problematic hoarding increase with age, beginning around 30 to 35, with the highest prevalence rates seen among individuals over 65,' said the researchers.
Research has shown that 42.9% of hoarders have depression (compared with 21% with OCD) and anti-depressants have been used with some success.
Teaching more positive thought patterns is also used. This may involve giving patients simple tasks such as clearing the kitchen and emptying bins, designed to help them get used to the act of cleaning and discarding.
One study found significant improvement after 26 sessions, while another showed nearly 70% were rated by their therapists as much or very much improved.
* For more information, visit mind.org.uk.
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