People often laugh at phobias or make jokes at the expense of those who suffer from mental and physical conditions.

But when nearly 20% of the population has some form of anxiety disorder it is no laughing matter.

Such is the spread of issues across the country that the figures have been compared by one charity to the amount of people suffering from heart disease or cancer.

Dr Marie Murphy, counselling psychologist, said: "The simplest definition of a phobia is a natural fear response which has become exaggerated or irrational.

"It is the natural fight, fight, freeze response which has become distorted probably because of an unpleasant experience.

"For example if you were bitten by a dog it would be rational to want to stay away from them. If you then can't bear to look at even a photo of a dog, it becomes irrational as it can't hurt you.

"Symptoms are physical - increased heart rate, sweating, shaking, sickness; psychological - irrational thinking, spiralling fear/danger based thoughts, eg this is going to kill me.

"Main coping mechanisms people start doing is to avoid the thing they are phobic about and everything associated with it.

"Phobias can come from childhood or adult experiences, although it may appear irrational there is always a reason for it."

Lynne Frederick, vice chair of the charity No Panic who help those suffering from anxiety problems, says: "It is hard to put a figure on how many people are suffering a phobia.

"One reason is because anxiety disorders e.g. phobias are all put under mental health.

"More women than men suffer from mental health problems and are more likely to have anxiety. One in ten adults have two or more symptoms of anxiety. Twenty eight per cent have mental health problems compared to 16% have heart disease and cancer.

"The second reason is many people don't go to their doctor with a phobia."

Mark Rees, No Panic membership secretary, told STV News that 18% of the population can have at least one phobia at any one time.

He added: "Of the Scottish people on No Panic's database 65.67% have a phobia of some kind we see a good range of that 18% in our work.

"So by some maths you could estimate that 18% of the 5.295 million Scottish people are anxiety disorder sufferers which would be 953,100 and No Panic's figures would put that 65.67% of those would have a specific identified phobia. So that would be about 625,900 people."

Nicky Lidbetter, CEO of Anxiety UK, said: "We conducted a survey of our membership some time ago that looked at the most frequently presented anxiety disorders (phobias being of course a form of anxiety disorder)."

Ms Lidbetter admitted the survey was carried out a few years ago, however, she added that "the issues that people are approaching us for support with aren't too different to what they were nearly ten years ago".

She said: "The key difference is that we now have many more people that approach us for help with health anxiety or what some people refer to as 'illness phobia'."

There are also complex phobias which include travelling on public transport, visiting a shopping centre or even leaving the house.

This can in turn lead to social anxiety disorder, where someone can have a fear of any general social activity.