When I recently found out I was pregnant, amid the terror I was feeling, I asked if I could go back home (I still think of the house I grew up in as home). I was terrified that I would sink into post-natal depression.

I'm 39 — middle-aged — and yet, I believe that my mum can make everything better and take away all my fears.

I drifted through my twenties and most of my thirties, unmarried, childless and ... I was going to say "independent". But it would probably be more accurate to say immature.

The truth is, I have never really been independent. I have always leaned on my mum.

According to research, I am not alone in this. My generation is one in which there is an abundance of thirtysomething and fortysomething kids who are still dependent, psychologically, if not financially, on their mums.

Slow on adulthood

So what are the consequences of being a thirtysomething or fortysomething going on 19? Does closeness with your mum make it difficult to grow up and take responsibility? First, if you do not think this is a generation of Peter Pans consider the following statistics.

In the Fifties, your life was mapped out for you. Becoming an adult involved a clear set of transitions, often taking place before your 21st birthday. You finished school, got a job, moved out of the home, married and had children.

In the Sixties, two thirds of all men and more than three quarters of all women had already attained financial and residential independence by the age of 30.

Today, a generation that has more choices than ever, fewer than half of all women and fewer than one third of men aged 30 have completed those transitions. We, more than any other generation in history, are prolonging childhood and postponing responsibility.

Increasing numbers of men and women born since 1970 have returned or have never left the family home, and there has been a large increase in the number of women who are waiting until they are over 35 or 40 to have a first child.

A growing phenomenon

A team of US social scientists recently concluded that a new period of life is emerging, in which people aged between 20 and 34 are no longer adolescents but nor can they be considered adults. The term "kidult" was coined to describe this growing group of people, who are technically adults but psychologically still children.

Psychologists have spent much time researching and commenting on mummy's boys but we don't hear much about mummy's girls. Yet, it appears to be a growing phenomenon.

Parent, not friend

An increasing number of women describe their mothers as their best friends. In his book The Mother Factor, clinical psychologist Stephan Poulter says this style of mothering has been on the rise for about 15 years and accounts for around 30 to 40 per cent of mothers. "Kids need a parent, not another friend," he writes.

But even for those who do not fall into this category, a close mother-daughter bond in adulthood, although it has benefits, can be problematic.

Take, for example, singer Cheryl Cole. It has been reported that she and her mother have always been close and that, after her wedding, Cole continued to lean on her mother, Joan.

Whether this bond contributed to the demise of Cole's marriage with Ashley, we can only speculate. But psychologists believe that having a wife's mother always at hand does not make for an easy married life.

According to Terri Apter, psychologist and author of You Don't Really Know Me: Why Mothers And Daughters Fight, for some women continued closeness with a mother is problematic. "Their life horizons threaten to contract as they monitor a mother's moods, worry about moving too far from her [either geographically or psychologically], keep watch on her approval or disapproval, and discover that inside their own head their mother's voice is a constant intruder," she says.

Though I have never regarded my mum as my best friend, I have begun to acknowledge that having such a close relationship can have its downsides.

For instance, I have never lived more than half-an-hour from my mum. But it is not just physical proximity that is an issue. When I mentioned my desire to live with my mum when I gave birth, my partner looked at me as if I was crazy.

Heeding the voice

Another downside is that I do feel that I have internalised my mum's critical voice. For instance, during my sister's pregnancy she had the occasional glass of refreshment in her third trimester. My sister dismissed my mum's disapproval, saying she was an adult.

I, on the other hand, know that even if I felt like having a glass of refreshment in a few months' time, I would sense my mum's condemnation and would abstain.

In her book My Mother My Self, Nancy Friday offers some theories on why many women find it difficult to separate emotionally from their mums. Much of the problem, she says, goes back to our childhood.

Protective attitude

The world, according to Friday, opens up before little boys. Through experience and practice, boys learn that accidents happen but are not fatal, rejections are lived through.

"Little girls, on the other hand, get the opposite training. The great, crippling imperative is that nothing must ever hurt my little girl. She is denied any but the most wrapped-in-cellophane experiences," she said.

Though I am grateful for the close relationship I have with my mum, when I look back I do think she was over-protective. In turn, I think this has made me struggle to grow up, psychologically speaking, and deal with the realities of adult life.

As Terri Apter stresses, a close relationship between mother and daughter in itself is not an impediment to growth.

She says: "If you can be close to a mother and still know your own mind — and speak it — if you do not mind displeasing her sometimes, then the closeness isn't holding you back, but may, in fact, be helping you thrive."

With that in mind, if the mood takes me, perhaps I should reach for that glass of refreshment after all.