While there is no single name for this experience — so let's call it "bed brain" — there are ways to combat these kinds of sleep-depriving thoughts. So why does our brain seem to cherrypick these random, and somewhat negative, thoughts as we are trying to fall asleep?

We're protecting ourselves

It may feel like your brain is tormenting you, but we do this out of the primitive need to protect ourselves. In hunter-gatherer times, and indeed now, if we weren't paying attention to the cliff or tiger ahead of us because we were distracted by a beautiful sunset, it could spell our demise.

So if you find yourself agonising over blunders made at work, it's likely you are assessing your performance and looking out for your livelihood.

It's a similar story if you fret over social acceptance, as being ostracised is processed in the same area of the brain that processes physical pain.

Mulling over how awkward you were at that party is likely your brain is assessing the "threat" of not being accepted.

This rather pessimistic way of thinking is referred to as the brain's negativity bias, which American neuroscientist Rick Hanson describes as "like Velcro for bad experiences but Teflon for positive ones".

This basically means our brains are really good at focusing on negative stuff, regardless of our positive experiences.

This kind of thinking doesn't just occur before bed. It can also be conditioned when we internalise voices such as those of critical parents, teachers and peers, as well as advertising that leaves us feeling like we're not up to standard. Typical thoughts would include 'I'm not good enough', 'I'm stupid/fat/ugly et cetera', 'I have to please people to get them to like me'.

Is this normal?

Pretty much.

Involuntary memories occur just as much as voluntary ones. We are just more likely to notice them when our brain is idle.

While some people may simply recognise negative thinking and move on, these thoughts can be perceived differently when someone is particularly concerned about something, or by people with clinical disorders such as insomnia, anxiety, depression or PTSD.

In these cases, people may perceive the thoughts as more distressing, ruminate or even suppress them (and the latter can potentially have the opposite effect and increase the frequency of these thoughts).

So why can it feel like all these thoughts come at once?

These memories are often being linked in a network, and hence activating one can result in others being activated. It would also be linked to the level of emotion … that can accompany these thoughts.

Poor sleep could be making it worse

Professor Sean Drummond is a clinical neuroscientist who specialises in sleep and mental health.

He says for many people, such as young parents or those who work long hours, the time before bed may be the only chance they have to reflect on the day.

This can see a backlog of thoughts come flooding in at once.

Not only can this thinking prevent you from sleeping, the negativity of those thoughts can be made worse if you are consistently not getting enough sleep.

"Sleep deprivation is known to increase the response of our emotional centres, especially to negative stimuli," Professor Drummond says.

He says it also decreases the strength of the connection between our brain's emotional centres and the part of the brain that is supposed to put the brakes on our emotions.

So prioritising and maintaining decent sleeping patterns is certainly one of the tactics worth giving a go.

Mindfulness and making time to worry

Mindfulness involves shifting the brain's attention and it can help thoughts to settle.

With mindfulness, you train your mind through observing it, rather than getting involved in the content of the thoughts, so it's like stepping back and witnessing your thoughts and feelings, without getting swept up in them.

One strategy is trying to pay attention to other things, like your feet on the ground or the points of contact of your body on the bed, or simply your breathing.

"Scheduled problem solving" or "scheduled worry" is another strategy.

This is where you set aside a specific period of time where you specifically engage in your worries and/or do your problem-solving for the next day.

It helps to write down solutions and insights. Then, if you start to worry at bedtime, you can say 'I already thought about that and have a plan. More worrying now will not help'.

If you're really struggling to calm down your thoughts at night, consider acupuncture.

Multiple studies have demonstrated acupuncture to be an effective treatment for insomnia. Acupuncture lessens anxiety, stimulates melatonin production, induces sleep onset, and reduce sleep disruption and arousal during the night. All of these effects amount to an overall increase in total sleep time and therefore a more positive outlook in general during waking hours.