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The psychology of adult thumbsucking

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Thumbsucking is a common, perfectly normal behaviour in babies and infants which most of us grow out of.

But what does it mean when thumbsucking continues into adulthood? We take a dive into the psychology of adult thumbsucking and the causes, consequences and side effects.

First off, let’s take a trip back to the womb….

You were thumbsucking before you were born

In a groundbreaking study in 2012, scientists from Durham university took a series of high resolution ultrasound scans of 15 unborn babies, to understand how fetuses prepare for life outside of the womb.

The images captured each baby thumb sucking in the womb, suggesting a deep, evolutionary basis for this behaviour.

For the first 3 years of an infant’s life, thumb and finger sucking is considered to be a normal part of infant development.

It gives the child a sense of relaxation, but it also contributes to the newborn’s facial growth, exercising the muscles involved in breathing, suckling and swallowing.

Studies have shown between 70% and 90% of children indulge in finger or thumbsucking, which is known scientifically as non-nutritive sucking (NNS).

Babies have an innate desire to suck and NNS is a way of exploring the world and helping to sooth and calm them.

It’s not just fingers and thumbs that work – sometimes it may be a pacifier, a flannel,  blanket, or a favourite toy. The adult version of this might be sucking on a pen, pencil or some even people that smoking cigarettes is a related behaviour.

How common is thumbsucking in adults?

Most children spontaneously give up thumb sucking between the ages of 2 and 4, but a certain proportion stick with the habit.

Between the ages of 7-11, around 1 in 8 children are still thumb or finger sucking, according to one survey by the British Orthodontic Society.

Very little data exists however on the prevalence in adults. Some anecdotal reports estimate around 1 in 10 adults suck their thumbs, but there’s little hard evidence, mainly it’s because people feel ashamed or embarrassed to admit it.

It’s been dubbed a silent phenomenon.

Adult thumbsucking online groups

Fortunately, despite the hidden nature of the topic there are places you can turn to online for guidance, support and discussion.

Thumb Sucking Adults is a website that’s been around since 1999. The content is qute old but there are tons of useful resources including articles, archives of emails from the community, opinion pieces, medical advice, photos and lots more. Probably the most authoritative user-based website on this topic.

Also, check out this quick 60 second documentary below, as it shows an adult thumbsucker living a perfectly happy fulfilled life.


There’s also a thumbsucking group on Reddit where you’ll find thousands of users posting topics such as ‘Does thumb sucking lead to stunted emotional development?‘ , My sister and I are proud thumb suckers, ‘Sucking my thumb makes me so happy, ‘A lifetime of thumbsuckingand hundreds more discussion threads.

These are just a few who are willing to talk about their thumbsucking habit openly online, so doubtless there are many, many more people out there.

Famous thumbsuckers – even celebrities do it!

In 2005,  Thumbsucker was released – an indie movie about a teenager coping with his thumb-sucking problem, his ADHD diagnosis and his romantic encounters.

With some big name celebrities including Keanu Reeves, Vince Vaughn and Tilda Swinton, the movie brought the topic into the mainstream, providing a fictional narrative to help shed light on the psychology of adult thumb sucking.

Since then, many celebrities have gone public, or at least they’ve been pictured in the media. Just google “famous thumbsuckers” and you’ll find celebrities sucking their thumbs including Madonna, Rhianna, Jennifer Lawrence and many more.

Thumb sucking celebrities
Famous celebrity thumb suckers. Clockwise from top left: Jennifer Lawrence, Victoria Beckham, Amy Winehouse (RIP), Geri Halliwell, Madonna, Rhianna

Sadly, the lack of male celebrities makes me conclude that this type of media coverage is more about sexualisation than destigmatizing the behaviour.

Regardless, seeing famous people indulge in public thumb sucking behaviour does help to diffuse and dispel the taboo around the subject.

What’s the cause of thumbsucking in adults?

Adult thumb sucking is a learned behaviour. This was observed in a 1960s experiment with kids comparing Freudian theory with learning theory.

A Freudian model would predict that kids temporarily deprived of being able to suck their thumb, would later on do it more, to make up for the lack of gratification.

A learning theory model on the other hand would predict the opposite – that prevention (wearing mittens for example) would lead to a reduction because the in­fant has not learned to ingrain such as habit.

It turned out the learning theory hypothesis was correct. With treatments such as positive reinforcement and/or aversive conditioning,  thumbsucking behaviour could be ‘unlearned’

Therefore the cause of adult thumbsucking is most likely a learned response originating from childhood. A way to seek comfort, a soothing behaviour that makes you feel safe and secure.

This might manifest in different situations, you may be relaxing, or alternatively it may be a response to stress or anxiety.

Thumbsucking, addiction and trauma

Some believe the psychological causes and consequences of thumbsucking are a manifestation of addictive behaviour.

And similar to biting your nails, twisting your hair – these childhood habits could become self-destructive addictions in later life such as overeating, smoking gambling or taking drugs.

This argument aligns with modern ideas about trauma response. Psychological trauma is broadly defined as a mental and/or physical response to stressful events.

And early-life trauma is very closely associated with addictive behaviours in later life.

So it’s certainly possible that the reason an adult never grew out of thumbsucking was rooted in some stressful childhood experience.

But whether or not all thumbsucking behaviour can be classed as a harmful addiction, the jury is still out on that one.

According to Freud what does thumbsucking show?

A lot of the shame, secrecy and hidden nature of adult thumb sucking can be explained by the legacy of Sigmund Freud. Considered the  “father of modern psychology”, Freud remains one of the most controversial and influential thinkers of the 20th century.

The inventor of psychoanalysis wrote volumes on just about every aspect of the human psyche, and often he conflated psychological problems and behavioural tendencies with repressed, hidden, often sexual desires.

In Three Contributions to the Theory of Sex, Freud discussed behaviours which on the surface, looked innocent and innocuous,  but, in his estimation were really forms of sexual activity.

One of these activities was thumb sucking. In this influential 1905 work, Freud wrote:

“I believe that the association of the manifestations into which we gained an insight through psychoanalytic investigation justify us in claiming thumbsucking as a sexual activity and in studying through it the essential features of the infantile sexual activity.”

“From the example of thumbsucking we may gather a great many points useful for the distinguishing of an erogenous zone. It is a portion of skin or mucus membrane in which the stimuluses produce a feeling of pleasure of definite quality.”
From Three Contributions to the Theory of Sex, (aka Three Essays on the Theory of Sexuality) Sigmund Freud 1905

These ideas might sound crazy and over the top in 2022, but Freud was a product of the Victorian era – a time of sexual repression, patriarchy and incredible sexism.

And in the time since this was written, most of his theories of psychosexual development – whereby thoughts and feelings are rooted in innate sexual desire – have been widely discredited.

But despite being widely discredited, Freud’s powerful legacy remains with us today, even in everyday language with phrases such as Freudian slip,” “repression,” and “denial”.

By associating finger or thumb sucking with sexual pleasure, Freud irreparably stigmatised the act into a psychologically complex, private, shameful activity.

Putting associations with oral sex aside, Freud is probably the main reason why adult thumb sucking is still sometimes talked about as taboo, perverse or a kind of sexual fetish.

Is thumb sucking bad for adults

Despite the social stigma, it’s not thought that there are any serious negative psychological effect of thumb sucking in adults. At the same time it’s not thought that there any real benefits of thumbsucking, apart from the psychological comfort gained from your habit.
Most adults are content to co-exist in a world where their behaviour may not widely socially accepted, but at the same time, it’s not regarded as harmful to anyone.
However, that said, there can be some serious issues that can arise if your habit gets out of control. Mostly these concern damage to the teeth.

Damage to your teeth and mouth

The most common effect of thumbsucking on teeth is misalignment, aka dental malocclusion.

This can cause an extended jaw, or overbite. It can even result in a ‘buck tooth” appearance, due to the continual pressure of the thumb on the front teeth.

You might also experience changes to the roof of your mouth, causing an indentation, or even soreness and sensitivity.

If you feel you might be at risk of any of these symptoms you should see your doctor or dentist straight away.

Other problems with your thumb or fingers

Other problems associated with long-term thumbsucking are to do with the digits themselves. Constant sucking can cause the skin to dry out, resulting in cracking skin or even bleeding. Also, you might see callouses begin to form.

Oral health is also an issue, in the worst case you might even experience an infected thumb from thumbsucking.

How to break a thumbsucking habit

So what do you do if you’re an adult who wants to stop sucking your thumb? Fortunately there are several solutions you can try.

Liquids and potions

Nail polish is something that many people consider as a preventative measure. It may work for some, but there are other, more effective alternatives available from Amazon and many other outlets.
This has over 1000 positive reviews on Amazon
Often you can try the same treatments that you’d find to stop adults fom nail-biting – bitter, stringent tasting liquids that discourage putting fingers or thumbs into the mouth

Lifestyle and habits

Another approach is to use tried and tested psychology techniques to break stubborn habits. There are many tactics you can employ such as goal setting:

  • trying to quit thumbsucking for just one day and then slowly building up
  • confiding with your friends and family to observe and gently guide you in the right direction if they witness you thumb sucking
  • positive reinforcement – give yourself a reward whenever you achieve a goal or a milestone in breaking the habit


Finally, although there’s still some societal stigma about seeking help, a psychology professional may be able to give you the right guidance if you feel stuck in a persistent habit you can’t break.

Cognitive behavioural therapy is an evidence based psychological treatment that’s effective for a wide range of problems including anxiety, depression and insomnia. CBT is based on tried and tested methods to identify and change faulty ways thinking and correct learned patterns of unhelpful behavior.

Hypnotherapy is another option and it works by changing automatic habits in the unconscious part of your mind. Hypnotherapy has been shown to be effective to help people stop smoking but it doesn’t work for everybody. However, for some it can be a fast, effective solution.


The psychology of adult thumbsucking is complex but ultimately rooted in childhood patterns of learned behaviour that spill over into adulthood.

Most people learn to live with their habit, although due to social taboos it largely remains a hidden secret habit, despite the fact that thumbsucking is a relatively benign and harmless activity.

Many adults are thumb suckers, but few like to talk about it. So don’t worry, you’re not alone!