Dementia is a serious loss of cognitive ability in a previously unimpaired individual.
Dementia occurs in the Dead Space series as a term to describe the psychological effects of the influence of the various Markers. It is characterized by vivid hallucinations, violent behavior, extreme paranoia, and other schizophrenic-like symptoms. It is often the result of a character's exposure to a Marker signal.
Symptoms and stages
Depending on the person, the symptoms are different and happen more quickly, depending on the length of the exposure to a Marker signal or the psychological state of the subject.
First stage hallucinations mainly consist of voices in the sufferer's head or visual hallucinations such as people. Depending on the situation, the hallucinations maybe be calm or violent. On the Sprawl, the children were reported seeing their dead relatives as a result of the Site 12 Marker's signal. However, sometimes the subject is already in such a poor mental state that they begin to immediately experience violent hallucinations; such as Nickolas Kuttner experiencing the death of his daughter again and again after touching a piece of Marker 3A. This was likely exacerbated further by his experiences as a marine. He also saw a number of calm hallucinations, including dying in a warm embrace with his daughter.
Second stage is when the subject begins to experience more severe hallucinations, such as monsters that are not really there or other horrifying experiences and voices that attempt to make the subject hurt themselves or others around them. Sometimes the hallucinations cause many people to commit mass suicide together. This is usually when the subject begins attacking others and possibly killing them in the process. After this action, the subject either shows no signs of regret or remembers nothing.
Later in the third stage, the subject begins to experience even more violent hallucinations. Depending on the person, these vary from either visual hallucinations to noise that drives the subject mad, often ending with them killing themselves. In Isaac Clarke's case, he starts seeing violent hallucinations of Nicole that make Isaac attempt to kill himself or cloud his sense of reality. Most people end up dead after this stage as a Necromorph outbreak has begun already due to the Marker signal affecting everyone around it. For unknown reasons, the signal can bring the subject in a state of coma temporarily, in a "dementia land" filled with shadowy figures and objects and sounds from the subjects past memories. The subject can also somehow physically die in these situations, possibly because they get killed by something in reality (in Isaac's case, he will shoot a Javelin spear into his head if he gets too close to "Nicole" at the end of Dead Space 2 in the "dementia land").
Sometimes the dementia does not cause the person to die but rather the Marker that inflicts it will make use of the subject in order to make more Markers by imprinting instructions to do so in their brains. This is the case with the smartest people affected and as a result, the hallucinations usually are less severe; mostly just voices or visual apparitions.
In Dead Space, the protagonist, Isaac Clarke suffers from dementia throughout the game. A vision of his girlfriend Nicole (who was already dead, unknown to Isaac) is the most serious of Isaac's symptoms. Dr. Terrence Kyne suffered a more serious form of this same dementia, thinking he was in the company of his wife Amelia, despite knowing that she had been dead for years. Kendra Daniels also may have been suffering from dementia, mentioning to Isaac that she had seen her brother (who was not present on the Ishimura and may be dead) on a security monitor. However, this could have been a ploy to garner sympathy from Isaac in order to further manipulate him. Zach Hammond made brief mentions of headaches and that he "thought he was seeing things", but otherwise seemed sane right up until his death.
Dead Space: Extraction
In the prequel, Dead Space: Extraction, the main protagonist, Nathan McNeill begins to suffer from dementia when not in Lexine Murdoch's presence. He sees non-existent Necromorphs and hears a woman singing "Twinkle Twinkle, Little Star."
Dead Space (mobile)
The protagonist Vandal has a very serious form of dementia. She occasionally sees visions of herself, which then transform into a Slasher when she approaches them. Sometimes, Vandal will be in one room, only to have her environment change to another, even to the extent of imagining she is in a desert near an alien Marker. She also sees Necromorphs that aren't real on numerous occasions, and even believes she is a Slasher herself at one point.
Dead Space 2
In Dead Space 2, Isaac's symptoms appear to be getting more severe and graphic; he often imagines his deceased girlfriend Nicole as decrepit and bloody, with a glow coming from her mouth and eyes. She often threatens him and, on more than one occasion, tries to kill him. When preventing her from stabbing him in the eye, Isaac soon realizes he is actually wielding the needle, showing the true severity of his illness. In the morgue of the Church of Unitology, Isaac can see multiple screaming corpses in the tubes. He also sees necromorphs that are not real, in some cases being flashbacks of events from the previous game, showing his occasional inability to differentiate between reality, his past, and his visions.
Dead Space 3
While Isaac doesn't show many symptoms in the main game, his ally, John Carver, does; if Dead Space 3 is played on Co-Op, Carver will experience many dementia moments revolving around the death of his wife and son. Some of the dementia moments involves him seeing his dead wife or hearing his dead son talk.
However, in Dead Space 3: Awakened after using the Codex and falling to the ground after the battle with the Tau Volantis Moon Isaac and Carver once again show signs of Dementia; the most notable and first being Isaac and Carver encountering a seemingly alive Norton, only to discover once they get close enough to him that Norton had long since transformed into a Necromorph. However, it is possible that these visions were the result of the Brethren Moons telepathic manipulations, as they repeatedly demonstrated the ability to cause Isaac and Carver to have hallucinations. Another example is the final hallucination confrontation (Final boss fight) Isaac and Carver get transported to the "Dementia Land".
- In Dead Space Mobile, when Vandal imagines herself as a Slasher, the player gets to play as a Slasher for a short period of time, which is the only time in the Dead Space series when the player is allowed to play a Necromorph in the main game. Though the player cannot attack or do any combat-specific actions, they can still walk and run. There are still remnants of what appears to be a black dress on her while she is a Slasher.
- As Isaac's Red Marker-induced dementia continues to corrupt his mind, the main menu adapts to show this through larger manifestations of marker pieces in Isaac's synapses as the player progresses; this is done to metaphorically show the worsening of his condition and to show that, as he regains his memories, the blueprints of the marker slowly begin to resurface (hence why Stross, who awakens sooner, can recall the text and the procedure to extract it earlier).
- Though referred to as dementia both in the game and by developers, the symptoms and effects more closely resemble those of schizophrenia. Damage to the brain such as those from dementia can cause these issues in one fashion or another, however the symptoms shown by those under the effects of Markers still share an uncanny similarity to those of schizophrenia, and not the clinical definition of dementia. However, schizophrenia typically causes auditory hallucinations, and visual ones are quite rare.
- In Dead Space 2, there is a text log entry done by a teacher telling of the children having "imaginary friends" as the log says. The kids would say that these "imaginary friends" were dead relatives. This is a result of the Marker's effect on the children's minds.
- While hallucinations are not commonly found in dementia sufferers, delusions are, which could mean that Isaac's diagnosis is plausible. This is because delusions (which are a variety of hallucinations) tend to involve belief in implausible events; these can range from realistic, such as the subject believing he is under constant surveillance, to unrealistic, like believing you can hear the dead (a symptom Nolan Stross has throughout, such as hearing the steps from his dead wife and son).
- Curiously, there is no evidence the soldiers of the S.C.A.F. detachment on Tau Volantis experienced hallucinations, despite being on a planet infested with Red Markers, although many of their forces did experience symptoms of dementia, from being driven to spoil the food supply to actually devouring necromorph flesh. John Carver was the only person on Tau Volantis to experience both dementia and hallucinations, until Isaac and Carver began experiencing them again following the destruction of Tau Volantis' Brethren Moon.