What can drive someone to insanity?
Certainly, insanity is something that is commonly understood (or misunderstood) and usually carries some sort of stigma in the popular consciousness. If you believe in modern psychology and psychiatry, there are literally thousands of forms of insanity that a person can end up developing over a lifetime. Some of them, like depression, are temporary, while others, like social anxiety, require more work for a person to get through. However, there appears to be some commonality as to what actually brings about most of the forms of insanity that people go through. Which brings the question to bear: is there a common, underlying trigger that compromises the stability of a person's mental health?
Things like stress and anxiety are often cited, as most of the common (and several uncommon) mental health issues are triggered by one of the two. Continued exposure to stress can eventually push someone beyond their “breaking point,” with the form of insanity afterwards being affected by external factors. This is often a long, strenuous process because most people have some level of resistance to such things, allowing them to at least survive the stressful period with their sanity intact. Additionally, the process may not even really result in insanity, with most of the population serving as proof of this theory. Prolonged stress can affect a person's behavior and outlook, but it is also known that several other factors can increase or reduce the impact of this. In some cases, stress and anxiety can merely even have the opposite effect, depending on the person's personal outlook.
Emotions are also said to play a critical role in driving or pushing people into insanity, with feelings being so closely tied to mental health. A person's emotional state can often be a reflection of a person's relative state of mental stability, but may also become an effect of fractured sanity. There is no doubting that emotions can disrupt and affect a person's thought processes and make them do things that they normally would not do. It has also been noted that extremely emotional situations and heavy emotional trauma can permanently affect a person's mind, often resulting in a condition that requires therapy to eventually overcome. However, it is rather arguable that emotions are merely augmenting the effects of stress and pressure, not a factor in itself.
Trauma is also frequently cited as having drastic effects on a person's sanity, particularly if it occurs during the formative years. The extreme psychological and emotional impact that trauma victims have to endure can often force some past the breaking point, having permanent effects on their mental health. However, it should be noted that trauma tends to be little more than a combination of stressful and emotional factors, usually mixed in with extreme circumstances. The vulnerability of the person's psyche plays a larger role here than in other potential causes of insanity, which explains why trauma encountered later on in life does not have the same general effect as similar events encountered during childhood.
Ultimately, insanity is something that, like sanity, must be defined on an individual basis. What is sane for one person in a given society may not be considered such by a different person within the same society. Insanity is a matter of context in this case, which is the assumption that some psychological texts make.