Status Effects were introduced in Alpha 12. They are applied to prisoners and have effects on them.
Well Fed
Prisoners who eat well will become "well fed", contributing to the good feeling in the prison. These prisoners are less likely to misbehave, and being well-fed contributes to the "Health" grading. The duration of this effect will increase with higher quantity and variety settings in the nutrition policy. You can get the "well-fed" status effect with Medium Quantity and High Variety, as well as High Quantity and Medium Variety, but to get the longest lasting effect you will need both High Quantity and High Variety.
Suppressed
Suppressed prisoners are much less likely to cause trouble. Spending lots of time suppressed also greatly improves both the "Punishment" and "Security" grading of the prisoner, greatly reducing their re-offending rate.
However, suppressed prisoners move slower. They are also less likely to be interested in different programs and when they do take part in programs, a high suppression rate during the lesson greatly reduces their attention-rating and thus their passing chance.
Prisoners can become suppressed by two different ways. The first is punishment, either Solitary Confinement or Lockdown. The second is proximity to Riot Guards, Armed Guards or Snipers who generate a 8, 12 or 30 tile suppression field. (The tile of guards themselves not included). In cheat mode, press F9 and check Influence to see the fields in blue. The amount of currently suppressed prisoners can be found by hovering the mouse over the Threat Level meter.
Tazed
Misbehaving prisoners may well get shot by a guard's tazer. This will apply the "Tazed" effect to the prisoner, who falls into an unconscious-like state that will gradually wear off. Unlike beating a prisoner unconscious, however, tazing a prisoner usually results in no injury. Some prisoners with the trait "Tough" have a chance of not going unconscious when tazed.
Surrendered
Armed guards will sometimes shout warnings to misbehaving prisoners before they open fire. An average prisoner may heed this warning and "Surrender", applying the status effect of the same name. Prisoners with the "Fearless" trait are less likely to surrender. Prisoners who have incurred the "Surrendered" status effect will stand still with their hands in the air until the effect wears off. Sometimes, a single warning shout or gunshot from an armed guard will cause multiple prisoners to surrender.
Calming
Prisoners who successfully complete the Spiritual Guidance program will receive the "Calm" status effect, which they may then pass on to other prisoners. This effect makes them less likely to misbehave, and will allow them to stop others from fighting.
Angry
Prisoners who have been denied parole will be Angry. This has the opposite effect to Calming, in that prisoners will be more likely to start a fight or attempt to escape.
Sick
When the virus event begins, a few prisoners in the prison will become sick, gain green heads and start vomiting with great regularity, and, if left untreated, eventually die. Prisoners will spread their disease to others nearby. To treat a prisoner, call a doctor or paramedic nearby, and their sickness "need" will begin decreasing. Some prisoners may need multiple treatments to completely remove the sickness, depending on its time untreated. A strategy to combat this is to immediately find the three or so infected prisoners once the outbreak starts and put them under permanent lockdown, perhaps placing a paramedic nearby each to treat them when needed, and wait for the disease to fade.
High / Drunk
A high or drunk prisoner acts in fairly similar ways, walking around slowly, bumping into walls, and being generally unproductive. If you see an intoxicated prisoner, it's worth giving them and their cell a search in case they're not done using the substance, so you can catch them in the act. The difference between being drunk and high, is that drunkenness can't hurt the prisoner, while a "high" level that is, in fact, too high, can lead to a prisoner overdosing, where they will need to be treated by a doctor semi-immediately or die. A guard will pick up an overdosed prisoner and take them to an infirmary for treatment, if there's one available. The alert for an overdosed prisoner is yellow and shows a bottle of pills. As one could likely imagine, drunkenness arises from the use of beer or, as it is called in-game, "booze", while being high originates from essentially every other narcotic a prisoner may steal except possibly cigs (untested).
Overdosed
An overdosing prisoner will die if not quickly healed by a doctor or taken to the Infirmary. When a prisoner is overdosing the player will be alerted with a green alert bubble showing the drugs icon. You can also hire a doctor where the overdosing prisoner is located, which may get the prisoner healed faster. Paramedics can also heal overdosing prisoners. The cause of overdosing is through over-usage of contraband needles or drugs.
Overheating
An overheating prisoner is caused by nearby hot temperatures like Kitchens or a Power Station. This is the opposite of Frigid. What about overheating from not having air conditioning place when the weather is very hot.
Frigid
A frigid prisoner is caused by cold temperatures. This is the opposite of Overheating.
As of Update 5c the prisoners no longer suffer the frigid effect from cold showers. Hot water showers are optional. If hot water is installed, the showers will provide benefits to comfort and warmth.
Riled Up
This occurs when the corrupting spiritualist event is played and the prisoners become angry, this is only temporary.