<unk> s can be caused by extreme pressure or irritation if no other mental disorder is discovered. The death of a loved one or a stressful life event can be enough to cause a<unk>  but conditions such as post-traumatic stress disorder and other psychiatric disorders have been known to cause<unk> s as well. If the individual is on medication, the<unk> s may be attributed to some side effects of the drug. Amphetamines, antidepressants, and stimulants like cocaine and caffeine can cause<unk> s. Blood pressure medication, levodopa and medications for Parkinson's disease have also been known to cause<unk> s. The<unk> s may be idiopathic or could be associated with psychiatric disorders like post-traumatic stress disorder, schizophrenia, and borderline personality disorder.<unk> s can also be triggered by stress and anxiety and substance abuse, such as drugs that affect the neurotransmitters norepinephrine and dopamine and serotonin. Nevertheless, causality between drugs such as beta-blockers or alpha-agonists and<unk> s is still unclear and further research needs to be done to investigate the biochemical mechanisms of<unk> s. Eighty percent of patients who suffer from PTSD report<unk> s. Patients suffering from PTSD have symptoms that are classified into three clusters: intrusive/re-experiencing, numbing, and hyperarousal.<unk> s are usually considered to be part of the intrusive/re-experiencing symptom. Some differences are existing between idiopathic and PTSD related<unk> s. A PTSD person having<unk> s would wake up during the night more frequently and for a longer time than with idiopathic<unk> s. Consequently, people with PTSD would have a poorer sleep quality. Furthermore,<unk> s related to PTSD would be more stressful than idiopathic ones. However, further studies have to be conducted in this area to obtain more reliable results.
Nightmare disorder
Exploding head syndrome
Idiopathic hypersomnia
Listener fatigue
Advanced sleep phase disorder
Circadian rhythm sleep disorder
Jurosomatic illness
Interictal dysphoric disorder