There are three main categories of tasks of a PTSD Service Dog:

1. Alerting
2. Calming
3. Helping with other co-morbid disabilities

A PTSD service dog is trained to perform specific tasks to assist individuals with post-traumatic stress disorder (PTSD).

These tasks fall into three categories:

• Alerting the individual to rising anxiety (before the anxiety gets too high). This task is by far the most important one for most handlers with PTSD. The service dog can be trained to recognize when the handler's anxiety rises (whether through noticing their increased heart rate, blood pressure, rate of breathing, or some other physical cue). The dog can then alert the handler before the anxiety rises too high, thus allowing the handler time to go to a less stimulating place (or start doing exercises to lower anxiety, such as deep breathing exercises). In time, the handler will be better able to tell on their own that their anxiety rate is increasing, and thus can reward the dog more clearly when the dog alerts them. Note that if the handler doesn't notice that their anxiety is rising until they have a full-blown panic attack, that is generally too late for the handler to do much about it. What's important is to have the dog alert them to rising anxiety early on so that the handler can stop the spiral before it goes out of control. 

• Calming the handler. A PTSD service dog can be trained to provide comfort and support to the individual during an episode, such as by providing deep pressure therapy or by sitting behind them ("Block" or "Cover My Six") to keep others from coming up behind them unexpectedly.

• Helping with other co-morbid disabilities. An example is roviding physical support ("Brace"), where the : The dog can be trained to assist the individual with physical tasks such as balancing, walking, or getting up from a seated position. With other disabilities, the service dog can support the handler's independence by the dog's training to  help the individual with daily tasks such as retrieving objects or helping with mobility, thus increasing the individual's independence and self-reliance.

Note: It's important to note that PTSD service dogs are specially trained to assist with the specific needs of an individual with PTSD (with their disability rising to the level as specified by the Americans with Disabilities Act) and are not to be confused with therapy dogs or emotional support animals.