Emotional stress
Working late night shifts
Traveling through different time zones
Having chronic diseases such as diabetes, kidney disease, lung disease, Alzheimers, or heart disease
Alcohol or drug use disorders
Gastrointestinal reflux disease
Heavy smoking
Work stress

Mechanism
Two main models exists as to the mechanism of insomnia, cognitive and physiological. The cognitive model suggests rumination and hyperarousal contribute to preventing a person from falling asleep and might lead to an episode of insomnia. The physiological model is based upon three major findings in people with insomnia; firstly, increased urinary cortisol and catecholamines have been found suggesting increased activity of the HPA axis and arousal; second, increased global cerebral glucose utilization during wakefulness and NREM sleep in people with insomnia; and lastly, increased full body metabolism and heart rate in those with insomnia. All these findings taken together suggest a dysregulation of the arousal system, cognitive system, and HPA axis all contributing to insomnia. However, it is unknown if the hyperarousal is a result of, or cause of insomnia. Altered levels of the inhibitory neurotransmitter GABA have been found, but the results have been inconsistent, and the implications of altered levels of such a ubiquitous neurotransmitter are unknown. Studies on whether insomnia is driven by circadian control over sleep or a wake dependent process have shown inconsistent results, but some literature suggests a dysregulation of the circadian rhythm based on core temperature.
Common misconceptions and expectations that can be modified include

Unrealistic sleep expectations
Misconceptions about insomnia causes
Amplifying the consequences of insomnia
Performance anxiety after trying for so long to have a good nights sleep by controlling the sleep processNumerous studies have reported positive outcomes of combining cognitive behavioral therapy for insomnia treatment with treatments such as stimulus control and the relaxation therapies. Hypnotic medications are equally effective in the short-term treatment of insomnia, but their effects wear off over time due to tolerance. The effects of CBT-I have sustained and lasting effects on treating insomnia long after therapy has been discontinued. The addition of hypnotic medications with CBT-I adds no benefit in insomnia. The long lasting benefits of a course of CBT-I shows superiority over pharmacological hypnotic drugs. Even in the short term when compared to short-term hypnotic medication such as zolpidem, CBT-I still shows significant superiority. Thus CBT-I is recommended as a first line treatment for insomnia.Common forms of CBT-I treatments include stimulus control therapy, sleep restriction, sleep hygiene, improved sleeping environments, relaxation training, paradoxical intention, and biofeedback. CBT is the well-accepted form of therapy for insomnia since it has no known adverse effects, whereas taking medications to alleviate insomnia symptoms have been shown to have adverse side effects. Nevertheless, the downside of CBT is that it may take a lot of time and motivation.Metacognition is a recent trend in approach to behaviour therapy of insomnia.