Intoxication (also known as substance intoxication) is an abnormal physiological and psychological state in an organism in reaction to exposure to mind altering or psychotropic substances, such as alcohol and recreational drugs of various kind. Exposure to an intoxicating substance usually occurs via ingestion of said substance, inhalation or dermal absorption. Intoxication manifests itself in many ways, including but not limited to slurred speech, loss of balance, loss of muscle control, irrational behavior, flushed skin, bloodshot eyes, erratic behavior, and loss of inhibition.
Alcohol intoxication, also known as drunkenness or inebriation, exhibits all of the aforementioned symptoms; it occurs when a person has had too much alcohol or ethanol in their bloodstream. The level of excess alcohol leads to physiological as well as psychological changes within an organism which can range from mild to severe, depending on the amount of alcohol consumed and tolerance of the organism to the alcohol. Polywater is another intoxicating substance. (TOS: "The Naked Time"; TNG: "The Naked Now")
In 2266 the USS Enterprise landed on Psi 2000, where the gravitational shifts associated with the disintegration of the planet resulted in the creation of large strings of water molecules known as polywater. A member of the landing party returned back to the Enterprise carrying with himself the intoxication associated with the polywater and unknowginly passed it on to others on the ship. In a short amount of time, everyone – while under the influence of the polywater – began exhibiting signs of severe intoxication to the point of engaging in self-destructive behavior. Spock also became very emotional and he and James T. Kirk, overcome by emotions, even began hitting each other at one point. Before the ship could succumb to complete chaos and eventual destruction, Doctor McCoy was luckily able to find a cure. (TOS: "The Naked Time")
Nearly a century later, in 2364, the entire crew of the USS Enterprise-D also became intoxicated by polywater, once again resulting in everyone acting out of character and exhibiting severe mania with little to no inhibitions. Geordi La Forge, for example, became very emotional, crying that he wanted to have normal vision again, while Lieutenant Tasha Yar seduced an equally intoxicated Data. Wesley Crusher sealed off main engineering as part of an experiment he wanted to conduct and declared himself "acting Captain Wesley Crusher". Doctor Beverly Crusher and Captain Jean-Luc Picard were close to crossing the line themselves, but luckily, she was able to find an antidote to combat the intoxication before the ship was destroyed by everyone's reckless behavior. Captain Picard compared everyone's behavior to drunkenness. It turned out that the SS Tsiolkovsky, which the Enterprise had been sent to investigate, and its entire crew had essentially intoxicated themselves to death after exposure to polywater. (TNG: "The Naked Now")
In 2374, Steth, a shapeshifter with the ability to steal the DNA of any humanoid form, switched places with Tom Paris and posed as the real one on board USS Voyager. Seven of Nine caught him with flushed cheeks and red eyes after he had replicated five alcoholic beverages in the mess hall alone. (VOY: "Vis à Vis")
In 2375, Seven became intoxicated after consuming just one glass of champagne at the christening of Voyager's quantum slipstream drive in engineering. After scanning her, The Doctor said "Apparently, the Borg can't hold their liquor." (VOY: "Timeless")
In the same year, Voyager was hosting Ambassador Tomin of the Kadi; a conservative race to whom formalities and proper etiquette as well as dispassion and aloofness in every aspect of life were highly valued virtues. Neelix, who was put in charge of Tomin during his time on board, made every effort to shield the ambassador from any kind of temptation to indulgences, but the ambassador was interested in anything but adhering to proper etiquette and dull diplomatic routines. On the contrary, he indulged in every vice he could imagine, one of which being consuming large amounts of synthehol. As a result he tumbled around the mess hall drunk during a diplomatic event bothering everyone, he came on to Seven asking her to assimilate him, and he even laughed at Tom Paris's jokes until he eventually passed out. Even though synthehol is not supposed to have the same effects on humanoids as real alcohol, in Tomin's case, theenzymes that break down synthehol were not present in his bloodstream. Tom Paris joked that he might need "a cold shower" to sober up but in the end Seven's nanoprobes were encoded to assimilate the synthehol molecules. (VOY: "Someone to Watch Over Me")
When in 2377, The Doctor was forced to hide his program in Seven's Borg implants, Seven, controlled by The Doctor, began consuming large amounts of alcohol and acted erratic, losing inhibition and her otherwise stoic Borg apathy. Seven herself was not at all pleased with what The Doctor had done to her body, but The Doctor wanted to at least once experience the sensation of being intoxicated with alcohol, among other things. (VOY: "Body and Soul")