We've all seen the headlines; it's the modern epidemic, costing UK industries billions. Some 91 million working days are lost annually to mental ill-health, and half of these are related to stress and anxiety.

Work isn't the only factor; events and circumstances in somebody's personal life, and other health conditions, for example, can also contribute.

And while certain things - like house moves, redundancy and exams - are recognised as being 'stressful', there's no way of measuring how much stress they'll cause and how this might affect one person from the next.

It can manifest physically too, suppressing the immune system and wreaking havoc with your sleep and digestive system.

Research suggests it can even affect memory function, and make us more sensitive to physical pain.

[Read more: What to eat to beat stress: Asparagus and 7 other foods to keep tensions at bay]

After BBC One's show, The Truth About Stress, in which Fiona Phillips explored why we're all more stressed than ever, we've highlighted some of the common signs to look out for:

Mood and character changes

When struggling with stress, it's usual to feel you've lost your patience, and find yourself being irritable and snappy. Long-term stress can increase irritability, aggression and anxiety.

Stress can lead to depression, poor concentration, and someone experiencing stress at work, for example, may struggle with seemingly simple tasks, including motivation, punctuality and decision-making. 

Feeling overwhelmed

Perhaps the clearest point that you've reached your stress tipping point is that desperate anxiety where you simply can't handle any more on your plate.

You feel at bursting point, and any additional demands sent your way - no matter how small they seem to others - are going to tip you over the edge or make you explode. Things you'd normally be able to handle now make you teary and afraid that you can't cope.

Excessive worrying

We're programmed to worry - it keeps us safe and functioning. But when you're suffering with stress, it's not unusual to find you're suddenly worrying much more about everything, and possibly having more negative thoughts than usual about things that may happen in the future, which may be a symptom of anxiety too.

Behaviour changes

Sometimes, though we may not even be aware we're doing it at first, stress can make us change our behaviours. This might be disengaging with hobbies, avoiding socialising, losing interest in things and neglecting physical appearance.

Sometimes people might start drinking more, using drugs or binge-eating, for example, too.

Sleep disturbance

"Stress makes it incredibly difficult to 'switch off' our brains, hence it is difficult to fall asleep and stay asleep," says Mel Wakeman from Birmingham City University's Faculty of Health. "Our normal sleep cycle gets disrupted, so we do not enter the essential deep phases of sleep. It's a vicious cycle, as less sleep means we are less able to cope with everyday stresses."

Exhaustion

Poor sleep inevitably leads to feeling drained the next day, but stress hormones can add to daytime fatigue too.

"When we're stressed, our body is wired and this means our metabolism's running at a faster rate. This will have the effect of draining our energy stores, hence we feel tired," adds Wakeman.

Stress

Palpitations

"Sometimes adrenalin can trigger our heart to beat very fast. It can be alarming and make you feel quite odd [pounding chest, heavy legs, light-headed]," says Wakeman.

Palpitations - being suddenly more aware of your heartbeat or feeling your heart's racing, pounding or fluttering in your chest and throat - can be very frightening, but it's a common symptom in stress and anxiety and, most of the time, harmless. If you're concerned, get it checked with your GP.

Dizziness

Feeling light-headed and dizzy can happen alongside palpitations, possibly as a symptom of a panic or anxiety attack. It can also happen on its own.

"Vasovagal syncope is most commonly associated with emotional stress and the impact it has on the nervous system," notes Nuffield Health physiologists.

"Triggers include perceived stimuli, like the sight of blood for instance, which cause an increase in parasympathetic drive and subsequent drops in blood pressure and/or heart rate, thereby momentarily disrupting blood supply to the brain."

[Read more: 10 quirky stress busters]

Weight loss or gain

Some people gain, while others lose weight when they're stressed. This may be linked with a loss of appetite, or comfort eating, and may also be due to metabolic factors associated with stress-induced hormonal changes.

Muscle tension

"Stress can also increase muscle tension, most commonly experienced via contraction of muscles in the upper limbs, neck and around the skull," says Horsley. This can contribute to an increase in general aches and pains, as well as feeling 'hunched' and tight.

Headaches

Muscle tension is also a factor in headaches, as are the increased levels of stress hormones. "These affect brain chemistry and lead to less control over blood vessel regulation," says Horsley. "This leads to inflammation and the associated pain of headaches, alongside a reduced capacity to process sensory information, such as sound and light."

Being run down, or existing health conditions worsen

"Prolonged stress is linked with higher levels of cortisol and we know this chemical reduces the activity of our immune system, making it more likely we pick up bugs," says Wakeman.

You may find you take longer to shake off colds and infections, and they wipe you out more. Plus, stress can worsen symptoms, or 'trigger' episodes of pre-existing health conditions, particularly things like irritable bowel syndrome (IBS), psoriasis, or autoimmune diseases like rheumatoid arthritis.

Catch The Truth About Stress on BBC iPlayer.