CAROLINE AHERNE’S LATEST weapon in her battle with depression and alcoholism is residential hospital treatment. Last autumn she checked herself into the £2,500-a-week Priory clinic in West London for a three-month stay over Christmas, New Year and her birthday. After a brief spell back home she was readmitted in February and has only just come out again.

But are such regimes the best way to overcome the type of problems she’s experiencing? In the field of the effectiveness of therapies, the bible is What Works For Whom? by Anthony Roth and Peter Fonagy of University College London. The book says 12 studies have found that inpatient treatment is no more successful than outpatient treatment. A further five studies show that it makes no difference how long you stay in hospital.

Despite seclusion from the temptation of pubs, off-licences and drinking chums; despite having all practical needs catered for; and despite intensive daily therapy, alcoholics who stay in hospital are no more likely to stay off the booze when they come out than those who continue to live at home. Two thirds of them will be back on the bottle inside six months.

You would not expect the dozens of celebrities who dry out in these luxury clinics to be aware of this evidence. But you would think they might wonder if the treatment was working when some keep going back for more. It’s almost as if they have become addicted to being in clinics: and in fact, although we cannot speculate on the reasons underlying Aherne’s problems, when you know more about the psychology of addicts, this is not such a silly idea.

Although hardly a week passes without some expert claiming that addiction is an inherited trait, the evidence from studies of twins and adopted children is far from clear. While genes may be crucial in some cases, childhood experience is usually the key. The main contributory factor is parental care: even if there is such a thing as a predetermined genetic vulnerability, your childhood history determines whether you will succumb to it.

Severe maltreatment, such as being beaten, sexually abused or emotionally neglected, is four times more common in addicts than in the healthy. Above all, most alcoholics were deprived of love and attention as babies. When they needed to be fed or cuddled that need was not met, leaving them feeling worthless and hopeless.

In later life, the feelings are still there. When they discover the rapid elation that the first drink brings, they have discovered the secret of life. Drinking themselves into oblivion becomes a way of drowning sorrow, a totally reliable, anti-depressant mother’s milk for which they do not have to be kept waiting because it is self-administered on demand.

Most alcoholics also suffer from depression, and they drink because they’re depressed. Alcohol goes on to wreck their lives, rotting their bodies and minds, adding to the depression and destroying their careers — as Oscar Wilde pointed out: “Work is the curse of the drinking classes.” But in most cases it is the depressed mood and thoughts that are the fundamental cause of this decline, not the drink alone.

The attraction of places such as the Priory is that their therapists look after the baby who is still desperately craving personal nurture and intimacy. Here is a place where the food comes at reliable times, where there are legions of staff to sympathise with your moods and a ready made community of the similarly afflicted. Perhaps above all, such places provide a structure, a scaffolding around which to arrange the addicts’ day.

They will have to attend daily group patient sessions to discuss their problems at ordained times. They will be given a selection of extra-curricular activities to fill their time between therapy sessions. They will have nurses and other patients to whom they can turn if they are feeling vulnerable.

This is incredibly helpful if you are desperate for a way to distract yourself from drinking, but it is also vital for someone who lacks internal scaffolding. A weak sense of self, also called Personality Disorder (PD), is a common problem for alcoholics, even before they discover booze. People with PD tend to have erratic moods and are prone to wild and unrealistic ideas.

That may be very helpful in writing or performing, but gets in the way of normal life, making them unstable friends and lovers. They may also be tremendously self-obsessed and have grandiose notions of their own worth and omnipotent fantasies of their powers (yes, many politicians do have symptoms of PD).

Architecturally, the Priory is a large, grand house in the Georgian style, like an aristocrat’s country seat. There is a “geographical fallacy” in the desire to get away. In a novel, when human emotions are attributed to something that is incapable of displaying them (“even the skies wept . . . ”) it is known as the pathetic fallacy. So it can be with moving from home to hospital: the illusion that because you are in a different place you will be a different person.