Many parents will feel a twinge of concern if their 5-year-old can't sleep without his dummy or their teenager refuses to throw out the tattered blanket she's had since she was a baby.
The topic of comfort objects is hotly debated, with some arguing attachment to objects from babyhood is childish, unnecessary or even harmful.
So when should you worry about your child's reliance on comfort items? And how can you encourage them to let go?
The truth is that even adults have attachment objects. How many get comfort from a favourite jumper? Or hoard treasured objects from loved ones without second thought?
A need for comfort is part of being human, and comfort objects remind us of feeling calm, secure and loved. Babies are born wanting to be held close.
They spend months cuddled and swayed, knowing someone will help soothe their needs. This helps them build feelings of secure attachment to a parent and confidence to go out into the world.
And one day they must make that journey — whether to childcare, school or even just across the room when they start to crawl.
A parent can't always be there to comfort them, but something that reminds them of that security can — a comforter, or, in scientific terms, a "transitional object" that bridges a link between a new situation and the comfort of home.
Although research in the 1940s considered such items a sign of poor attachment, the paediatrician and psychoanalyst Donald Winnicott later proposed that they were, in fact, the opposite. Rather than being an object to turn to in lieu of love and care, they were a reminder of love and security.
One study found kids with strong bonds to transitional objects have stronger attachment to a parent.
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Although most children grow out of comfort objects by the age of four, later research has continued to back up Winnicott. One study found that kids with strong bonds to transitional objects have stronger attachment to a parent and are happier than those without.
But this effect starts to reverse as children get older. The same study showed that teens who still hold a strong attachment to a transitional object have poorer mental health.
While there is nothing wrong with keeping a comfort blanket for the fond memories it brings, still needing it on a day to day basis as a teenager, or indeed as an adult, could be a sign that something is wrong.
Dummies and bottles
Some comfort objects, however, are better than others. The evidence for using dummies or bottles past 12 months is less positive. Similarly, although babies thumb suck in the womb, if this habit is carried on past a year, problems can arise.
Babies are born with an innate need to suck. When breastfeeding, sucking feeds them, calms them and increases the mother's milk supply. Dummies can help bottle-fed babies to suck and calm themselves.
Sometimes breastfeeding mums use them, but if a baby meets its sucking needs elsewhere, this can reduce milk supply, so they aren't recommended in the first six weeks.
The subject of using a dummy can be divisive. If they're used carefully, they can benefit young babies and are recommended at night as they may reduce Sudden Infant Death Syndrome risk. Sucking can also sometimes help a baby with colic.
But experts recommend babies should be weaned from dummies after six months. Aside from the challenge of weaning an older baby, dummies can introduce harmful bacteria into the mouth. They can also increase the risk of ear infections, and affect how teeth come through.
Allowing children to have a bottle for comfort is also a bad idea. Bottles are naturally associated with comfort due to the combination of food, sucking and being held close. But babies should be slowly weaned off them once they are eating solids and stopped by 12 months. When a baby sucks on a bottle, the milk pools around their teeth and can cause cavities.
The same does not apply to breastfed babies. There is a lot of difference in pliability between a nipple and a dummy or bottle, meaning less impact on jaw and tooth development.
Nipples are also not kept in the mouth for extended periods. Finally, breastmilk is delivered to the back of the mouth rather than milk pooling around the front teeth meaning a lower risk of cavities.
So those who squirm at the thought of breastfeeding past infancy but encourage a dummy are not only confused in their logic (after all, a dummy is a fake nipple) but the outcomes are potentially worse.
Weaning babies from dummies and bottles is best started early, rather than letting it become an ingrained habit.
Start by removing it during the day and try to offer something positive — more hugs, a book and a cuddle, or a distracting toy if they become upset. Toddlers can be persuaded with sticker charts, or swapping their dummies with the popular "dummy fairy" who brings a new toy for the "big girl or boy" instead.
To wean from bottles, offer babies a cup of water with meals from six months old. Once they have the hang of a cup, slowly swap bottles for cups over a few weeks.
The night-time one can be the hardest so try to adopt a new routine to calm them which doesn't involve them feeding to sleep.
In short, comfort objects are normal and a great way for small children (and occasionally grown-ups) to calm and soothe themselves, and there is no need to worry about removing them. But once they can walk and talk, stick to the cuddly (or toy car) variety rather than a dummy or bottle — not least for your sanity when it comes to weaning.
• Amy Brown is associate professor of child public health, Swansea University
- The Conversation