Mental illness can affect how people subjectively perceive and navigate the outside world. Certain disorders are frequently connected with heightened sensitivity to feeling rejected, criticised, or prone to failure. They may also lead to intense and overwhelming feelings of positive experiences, such as enthusiasm or joy, as well as the same exceptionally strong feelings when experiencing anxiety or shame.

Clinicians have noted that people living with depression and borderline personality disorder often experience negative emotions more powerfully and find less satisfaction in typically enjoyable events. To find out whether this might extend to perceptions of taste, a team of researchers including Gonzalo Arrondo undertook a study examining how people rated sweet, bitter, and neutral flavours.

Participants were asked to take a sip of, but not swallow, one of three options. Those who were given a sweet option were given orange juice. Quinine, which is used as a flavouring in drinks such as tonic water and bitter lemon, was used on its own to serve as a bitter taste. The final group was given water, which served as a neutral comparison for the other two taste categories. After holding the drinks in their mouths for five seconds, participants were asked to rate the disgust and pleasantness of the liquids.

There were no significant differences in taste perceptions for those with depression. However, the research team found that participants with borderline personality disorder rated both the bitter and sweet tastes less pleasant and more disgusting than the neutral taste. Additionally, participants with borderline personality disorder experienced increased self-disgust after experiencing the sweet taste.

These results suggest that abnormal sensory processing and self-identity may be closely linked in people with borderline personality disorder. In fact, the research team has speculated that in borderline personality disorder, self-disgust is heightened to a degree that may cause it to impair the enjoyment of typically pleasant stimuli. Thus, these findings draw attention to the importance of considering both internal and external disgust when diagnosing and managing borderline personality disorder.

Written by Anjalene Whittier.

Cover image: “Watermelon Summer” by Jill111 licensed under CC0 Public Domain (resized and cropped to fit)