After experiencing a stressful event, it's natural to have lingering feelings of unease and perhaps trouble sleeping for a short time afterwards. In most cases, things return to normal after a little while, and even though memories of the event remain, people are able to get back to living their life without problems.

In some cases, however, such an event can be the cause of a serious mental health condition: post-traumatic stress disorder, or PTSD. PTSD sufferers are unlikely to get better without counselling and other professional help, so it's important to recognise if you may have it. Here are the things to look out for.

A triggering event

In order to be classed as PTSD, there needs to be some sort of event that triggers it. The nature of these events can vary drastically, but they include being a victim of a crime, witnessing a distressing occurrence, involvement in a car accident and being present during a natural disaster. They're not always single events, either; some people experience post-traumatic stress disorder after prolonged stressful occurrences.

If you have symptoms without such an event, it's still important to seek help, as you may be suffering from another form of mental illness.

Disturbed sleep and nightmares

Part of constantly thinking about and reliving the event is often an inability to sleep. When you do manage to fall asleep, it's likely that you'll have bad dreams about the traumatic event, as it's on your mind beforehand.

Flashbacks

Flashbacks are one of the particularly distinctive symptoms of PTSD, and one of the worst for many people. These experiences are almost like waking dreams, where you relive the event almost as though it's happening again. They can be triggered by things that remind you of it, and avoiding these factors can be difficult since they're not always easy to predict.

Depressive symptoms

It shouldn't come as much surprise that depression is a frequent part of PTSD. Irritability, social isolation, weight gain or loss and emotional instability are all symptoms related to being depressed.

Panic and anxiety

With anxiety levels higher in people with PTSD, you may experience panic attacks and irrational anxious feelings. These are sometimes related to places, people, sounds, smells or sights that remind you of the traumatic experience you had. Other times, social situations or crowds might be the cause or, conversely, being left alone may trigger anxiety. Panic attacks involve a range of symptoms, but the most common are difficulty breathing, pain or tightness in the chest, visual disturbances and a pounding heart.