The causes of teeth grinding (bruxism) aren't always known, but it's usually linked to other factors, such as stress and anxiety or sleep problems.

Stress and anxiety

Teeth grinding can be associated with mental or psychological problems, such as stress and anxiety.

Studies have shown around 70% of cases of sleep bruxism are caused by stress or anxiety, which affects people subconsciously while they're asleep.

High levels of work-related stress can have a significant adverse affect on your sleep and trigger episodes of sleep bruxism.

Being stressed or anxious may also cause you to clench your jaw or grind your teeth. 

Bruxism can also sometimes be caused by taking certain antidepressants used to treat depression and anxiety.

Sleep disorders

Studies have shown people who snore or have a sleep disorder, such as obstructive sleep apnoea (OSA), are more likely to grind their teeth while they're asleep. OSA causes your breathing to be interrupted while you sleep.

The link between bruxism and OSA has only been identified fairly recently, and the exact relationship between the two conditions isn't fully understood.

You're also more likely to grind your teeth if:

• you talk or mumble while asleep
• behave violently while asleep, such as kicking out or punching
• you have sleep paralysis (a temporary inability to move or speak while waking up or falling asleep)
• you experience hallucinations (seeing or hearing things that aren't real) while you're semi-conscious

Medication

Bruxism can sometimes occur as a side effect of taking certain types of medication. These include some psychotropic medicines that affect your mood, such as antidepressants and antipsychotics.

In particular, bruxism is sometimes linked to a type of antidepressant known as a selective serotonin reuptake inhibitor (SSRI). Examples of SSRIs include paroxetine, fluoxetine and setraline.

Although there's an increased risk of developing bruxism if you're taking these medications, you may not develop any symptoms.

Lifestyle

Certain lifestyle factors can also increase your chances of developing bruxism. These include:

• drinking alcohol excessively
• smoking
• using recreational drugs, such as ecstasy and cocaine
• drinking caffeinated drinks, such as tea or coffee (six or more cups a day)

Teeth grinding in children

Around 1 in 5 children up to the age of 11 are reported to have bruxism, although the real figure is probably higher as it's often not noticed by parents.

Teeth grinding often occurs after a child develops their first teeth and again after they develop their permanent teeth. The habit usually stops after the adult teeth are fully formed.

After teething, a child may grind their teeth for the same reasons that adults do. For example, it may occur at stressful times, such as during school exams.