Low doses can result in psychological effects of "mild euphoria, alertness, and enhanced cognitive performance"; higher doses produce physiological side effects of nausea, anxiety, trembling, and jitteriness. There are individuals who are prone to caffeines anxiogenic effects whilst others are susceptible to its caffeine-induced sleep disturbances and insomnia. Studies with twins have shown that genetics influence individual differences in response to caffeine. Homozygous twins have been found to react in more consistent ways to the caffeine than heterozygous twins. Behavioral effects
Caffeines widespread appeal is due primarily to its mild psychostimulant properties, which increase alertness and cognitive arousal and diminish fatigue. Caffeine also produces a wide range of other symptoms, including upregulation of the cardiovascular system, increased global cognitive processing, and improved physical functioning. Cardiovascular effects can range from increased heart rate and reactivity to severe cardiac arrhythmia. The cognitive effects of caffeine include increased performance in memory, attention, and text reading. The physical effects of caffeine include lowered sensations of pain, less perceived effort, and increased muscle strength and endurance. However, at doses above ~400 mg, both cognitive and physical performance begins to worsen and symptoms of anxiety increase. One study that explored ad lib caffeine consumption in 159 college students found that high consumers reported lower academic performance. The same study also concluded that moderate and high consumers combined reported significantly higher trait anxiety and depression scores when compared with abstainers. These anxiety symptoms include persisting insomnia, nervousness, and mood fluctuations.When undergoing stress, the body activates a system-wide response mechanism known as the HPA axis.
Diffuse idiopathic skeletal hyperostosis (DISH) is a condition characterized by abnormal calcification/bone formation (hyperostosis) of the soft tissues surrounding the joints of the spine, and also of the peripheral or appendicular skeleton. In the spine, there is bone formation along the anterior longitudinal ligament and sometimes the posterior longitudinal ligament, which may lead to partial or complete fusion of adjacent vertebrae. The facet and sacroiliac joints tend to be uninvolved. The thoracic spine is the most common level involved. In the peripheral skeleton, DISH manifests as a calcific enthesopathy, with pathologic bone formation at sites where ligaments and tendons attach to bone. Signs and symptoms
The majority of people with DISH are not symptomatic, and the findings are an incidental imaging abnormality. In some, the x-ray findings may correspond to symptoms of back stiffness with flexion/extension or with mild back pain. Back pain or stiffness may be worse in the morning. Rarely, large anterior cervical spine osteophytes may affect the esophagus or the larynx and cause pain, difficulty swallowing or even dyspnea. Similar calcification and ossification may be seen at peripheral entheseal sites, including the shoulder, iliac crest, ischial tuberosity, trochanters of the hip, tibial tuberosities, patellae, and bones of the hands and/or feet.DISH can be a complicating factor when suffering from trauma involving the spine. It increases the risk of unstable fractures involving the intervertebral disc and the calcified/ossified ligaments which influences the need for surgical treatment. Cause
The exact cause is unknown. Mechanical, dietary factors and use of some medications (e.g.