1. You haven't slept
Ever feel things wouldn't seem quite so bad if you'd had a good night's slumber? It's highly likely your ability to regulate your emotions has been compromised by fatigue, says a study from Tel Aviv University.
'It turns out we lose our neutrality,' says Professor Talmer Hendler, who led the research. 'The ability of the brain to tell what's important is compromised. It's as if suddenly everything is as important.'
The solution, of course, is to take steps to improve your sleep quality. Aim to go to bed at the same time every night, turn off TVs and computers at least an hour before bedtime and steer clear of caffeine and alcohol in the evenings.
Related: Get more sleep tips
2. You're feeling hungry
Fluctuations in levels of the feel-good hormone serotonin, which often occur when we haven't eaten, can affect our ability to regulate anger, according to researchers at the University of Cambridge.
Another recent study at Ohio State University suggests that couples are more likely to argue with one another on an empty stomach.
Researchers found that blood glucose levels in married people, measured each night, predicted how angry they would be with their other half that evening.
People who eat a lot of refined sugars – found in sweets, cakes and biscuits – are more likely to experience these fluctuations. The trick, of course, is to regulate your blood sugar levels by adopting a healthy, balanced, nutrient-rich diet. And never skip meals!
Related: 10 ways to cut down on sugar
3. You haven't drunk enough water
Not feeling thirsty? That's no excuse. Even mild dehydration can significantly alter your mood and ability to think clearly, say researchers at the University of Connecticut.
'Our thirst sensation doesn't really appear until we are one or two per cent dehydrated,' explains Lawrence E Armstrong, one of the study's lead authors. 'By then, dehydration is already setting in and starting to impact how our minds and bodies perform.'
Everyone's fluid needs vary, due to factors such as size and activity levels – but as a general rule, you should aim to consume around two litres of water each day. Get more information from the British Nutrition Foundation.
Related: How much water do you really need to drink?
4. You've been staring at a screen all day
Many of us like to keep ourselves entertained and informed by watching TV or looking at social media sites, such as Facebook – and that's fine. However, it's worth bearing in mind a growing body of research that suggests too much screen-time may be having an effect on our anger levels.
A couple of examples? Facebook can make us 'lonely and angry', partly because it helps foster the idea that everyone else is having a much better time than we are, say researchers at Denmark's Happiness Research Institute. They found that regular Facebook-users who stayed away from the site for a week became significantly less angry.
Other studies have suggested that watching violent TV shows could make both children and adults tend more towards aggression, although the evidence is mixed.
A report from the International Society for Research on Aggression concluded that exposure to media violence is one risk factor for increased aggression in both the short and long term.
5. It's your hormones
Hormone fluctuations, particularly the gradual dip in oestrogen levels in the lead-up to the menopause, can make us more likely to fly off the handle at the slightest provocation. Low oestrogen may also lead to mood swings and make it harder to cope with stress in general.
Around 60 per cent of perimenopausal women suffer from low mood, and women in their fifties seemingly most affected, according to a recent survey for Healthspan.
Getting plenty of sleep, taking regular exercise and eating a healthy, balanced diet can all make a big difference – but do consult your GP to discuss other potential treatments and strategies to address the problem.
Related: Got the moody blues? Read more about the causes of mood swings in women