<unk>  can produce tunnel vision, making it difficult to read multiple gauges. Due to its perception-altering effects, the onset of<unk>  may be hard to recognize. At its most benign,<unk>  results in relief of anxiety – a feeling of tranquillity and mastery of the environment. These effects are essentially identical to various concentrations of nitrous oxide. They also resemble (though not as closely) the effects of alcohol or cannabis and the familiar benzodiazepine drugs such as diazepam and alprazolam. Such effects are not harmful unless they cause some immediate danger to go unrecognized and unaddressed. Once stabilized, the effects generally remain the same at a given depth, only worsening if the diver ventures deeper. The most dangerous aspects of<unk>  are the impairment of judgement, multi-tasking and coordination, and the loss of decision-making ability and focus. Other effects include vertigo and visual or auditory disturbances. The syndrome may cause exhilaration, giddiness, extreme anxiety, depression, or paranoia, depending on the individual diver and the diver's medical or personal history. When more serious, the diver may feel overconfident, disregarding normal safe diving practices. Slowed mental activity, as indicated by increased reaction time and increased errors in cognitive function, are effects which increase the risk of a diver mismanaging an incident.<unk>  reduces both the perception of cold discomfort and shivering and thereby affects the production of body heat and consequently allows a faster drop in the core temperature in cold water, with reduced awareness of the developing problem. The relation of depth to<unk>  is sometimes informally known as "Martini's law", the idea that<unk>  results in the feeling of one martini for every below depth. Professional divers use such a calculation only as a rough guide to give new divers a metaphor, comparing a situation they may be more familiar with. Reported signs and symptoms are summarized against typical depths in meters and feet of sea water in the following table, closely adapted from Deeper into Diving by Lippman and Mitchell: + Signs and symptoms of<unk> , breathing air Pressure (bar) Depth (m) Depth (ft) Comments 1–2 0–10 0–33 2–4 10–30 33–100 4–6 30–50 100–165 6–8 50–70 165–230 8–10 70–90 230–300 10+ 90+ 300+
Nitrogen narcosis
Malignant hyperthermia
Anoxia
Barbiturate overdose
Histotoxic hypoxia
Pseudohypoxia
Hypoxia 
Hypothermia