It's a term which has yet to enter official psychiatric classification.

But like other forms of emotionally dysfunctional behaviour, sexual anorexia is very distressing for those caught up in it.

And like the eating disorder anorexia nervosa, secrecy is a big component to sexual anorexia.

Sex is a normal and healthy part of adult human life, yet there are people who are afraid of their own sexual appetites. They are afraid to give in to it.

Such people can go on for years hiding from their friends and loved ones the fact that they are avoiding sexual activity. This sense of shame from the sufferer makes detection, diagnosis and treatment difficult.

Sexual anorexia, like other conditions of sexual dysfunction, has many origins.

It could be a fear of intimacy or of losing control. Other sufferers have spoken of poor self-esteem in the sense that deep down, they cannot imagine anyone being sexually attracted to them.

Some, but not all, sufferers may have been abused as children and find it hard to incorporate healthy sexual activity into their adult lives.

Some sufferers are punishing themselves for a real or imagined transgression, so they deny their natural sex drive.

Others have experienced physical difficulties during intercourse and sex has become something painful for them, or they have developed a phobia of it.

Often, the sufferer wants to be in a loving relationship, or even get married one day and have children, but the avoidance of sex gets in the way.

Such sufferers become skilled at avoiding sex. Their excuses vary from 'being tired' or 'having a headache' to pretending to have a period. They leave a date early because of 'work commitments', or manufacture a row to make their partners storm off.

Sometimes, sufferers aren't even aware that they have a problem. Each excuse seems valid to them but, over time, a pattern of avoidance emerges.

Psychotherapists see sexual anorexia as a form of compulsive, self-destructive, reality-avoidant behaviour. The concern is that if the condition goes untreated, it can cause problems with work, family, finances, and even personal safety.

Part of the reason for an increase in the number of sufferers is the way modern society functions.

With the Internet, mobile phone or text messaging, our interactions with other people have increasingly become impersonal.

We can be in a relationship without actually being in physical contact with the other person. Because of this, we run the risk of being very under-practised when it comes to having a real relationship with someone. Put simply, we lack the skills for true intimacy.

Of course, our libido, or sex drive, fluctuates over time, especially within the same relationship.

The so-called honeymoon period, when a couple are at it 'like rabbits', can never be sustained, no matter how much Viagra is consumed.

And there are also people who describe themselves and their sexual orientation as asexual, having the same emotional needs as others, and being attracted to others, but claiming to experience no sexual attraction. I would not use the term sexual anorexia for people in such a situation.

Few sexual relationships are consistently 'perfect'. Thankfully, most problems are short-lived. It is vital for anyone with a sexual problem to get help.

It's important to lay claim to your own sexuality, and be the fulfilled person you are entitled to be.

So learn to recognise when you are, or are not, in a mutually loving relationship. The secret of great sex has to do with what goes on inside your head.

Lucy Beresford is a writer and practising psychotherapist. Her novel, Something I'm Not, is published by Duckworths and due for release on Feb15 (see www.amazon.com).