Ketamine – a drug used primarily by doctors and veterinarians as an anaesthetic, sedative and pain-killer – is a promising therapy for people with treatment-resistant depression, producing a rapid and sustained decrease in depressive symptoms. The small study of French patients has also provided insight into the overwhelmingly optimistic view of the world that people tend to have.
The World Health Organization says depression affects five percent of adults worldwide and is a major contributor to the overall global burden of disease. Depression involves cognitive impairment that colours a person’s perception and interpretation of life events. People with depression view the world with pessimism, as worthless and hopeless. In this state of ‘pervasive pessimism,’ the person can also resist information that counters their highly negative beliefs about the future. Around one-third of people with major depressive disorder or bipolar depression do not have significant improvement even after months of treatment.
Ketamine’s impact on thinking patterns can be understood better when considering the way that healthy people think. When people make decisions, they usually first make some assumptions or guesses about the likely result of these choices. Research has previously found that humans have a strong optimism bias — most people will overestimate the likelihood of positive events, such as success in the job market, or winning a lottery. People also underestimate the likelihood of negative events such as being in a car accident, or suffering from cancer.
