Occaisionally some characters are seen wearing skimpy clothing, though not too severe. Often these characters work in the bar featured in the show. The woman running a gambling table shows a decent amount of cleavage. Sometimes characters are naked, but there is never nudity.

Frequent, moderate, stylized sci-fi violence.

The protagonists are military officers. The story prominently features a major interstellar war. Many grand battle scenes with stylized explosions of starships.

Many minor/irrelevant characters are killed, most of them by sci-fi weapons, some of them by stabbing. Protagonists occasionally kill humanoid aliens (in war situations, direct self-defence or in a duel).

Occasionally people get waporised by sci-fi weapons. In one episode it is implied that some people think it feels like being boiled alive.

A few mentions of rape and torture. One torture scene takes place:

In the episode "The Die is Cast" (3x21) A Cardassian (non-human but humanoid) secret agent uses a sci-fi device to lock a shapeshifter (one of the protagonists) into a human form when his biorythm would require him to revert into a liquid. (Sci-fi equivalent of sleep deprivation.) He's shown deteriorating and shedding "withered" flicks of his body. (He doesn't sustain permament injury though.) He agonises in pain.

A Klingon (non-human but humanoid) stabs his own brother at an unsuccessful attempt to ritually kill him at his own request.

Klingons often engage in violent games and brawling that seems excessive with human eyes (as they are stronger and tougher than humans).

Nearly no blood. Drops and vials of blood are shown, not related to violence. In the episode "Field of Fire" (7x13) a Vulcan (non-human but humanoid) criminal gets shot by one of the protagonists. He's shown bleeding mildly but his blood is green as he isn't human.

"D*mn" is used in almost every episode.

Religious profanity

Alcohol consumption frequently shown. (Many scenes take place in Quark's bar where people drink socially.)

Occasional drunkness of some protagonists. Heavy drinking by Klingons (non-humans but humanoids).

A hostile alien species called the Jem'Hadar are genetically engineered to be addicted to a synthetic drug, as a means to ensure their obedience and dependence of the Dominion. Taking the drug is shown a few times. In a few episodes their addiction is a plot element.

Deep Space Nine is darker and contains higher levels of emotional intensity and drama than other Star Trek shows. But it never gets to the point of severe. It's still very lighthearted when compared to scarier shows.

The story peripherially involves: racial opression, slavery, genocide, internment and concentration camps, ghettos (deceitfully called "sanctuaries") with humans in it, secret agents and spies, interrogations, organised crime, suicide, terrorism, weapons of mass destruction, possession by supernatural forces (both good and bad), mental illness, demon worshipping, suicidal cult, coup d'etait attempted by a human military officer, treason and theft committed by a number of defecting human military officers.

One torture scene (see in violence section). The background music extends the psychological effect.

The series feature a species of malevolent shape-shifters who have the ability to undistinguishably duplicate people and objects. Might be frightening for younger children.

A lot of alien species appear in the series, some of them (like the Letheans or the Jem'Hadar) may be frightening for younger children.

The episodes " ...Nor the Battle to the Strong" (5x04) and "The Siege of AR-558" (7x08) are "in the trenches" kind of war stories that may be too intense/realistic/dark for younger children. The latter involves a boy permanently losing a leg as result of a war wound.

The episode "Distant Voices" (3x18) may be particulary scary for younger children.

The episode "Hard Time" (4x19) contains high emotional tension, involves confinement, starvation, murder, family/social disfunctionality and suicidal intent.

There are a few other episodes - like "The Visitor" (4x03), "The Begotten" (5x12), "Dr. Bashir, I Presume?" (5x16) or "Time's Orphan" (6x24) - which are emotionally intense.