The current study investigates whether perceived time has an effect on blood glucose level in people with type 2 diabetes. The hypothesis is that perceived time will have a greater influence over blood glucose level than actual time. Changes in blood glucose levels were measured in 46 participants with diabetes while they completed simple tasks during a 90-min period. Participants' perception of time was manipulated by having them refer to clocks that were either accurate or altered to run fast or slow. Blood glucose levels changed in accordance with how much time they believed had passed instead of how much time had actually passed. These results are an example of the influence psychological processes can directly exert on the body. T he relationship between expectations and physiological responses has received much attention in the study of the placebo effect (1, 2), a phenomenon producing physiological changes in the body without specific biological stimulation (3). For example, the expectation that an activity leads to a decrease in weight may result in an actual reduction of weight (4), and perceptions also change physiological responses to food consumption (5). Similarly, study participants role-playing air force pilots, a group expected to have excellent vision, had better vision than control participants (6). Despite a broad range of data describing the influence of mental states over the body, the role of psychological processes, especially when dealing with chronic health conditions, has been frequently underestimated. The connection between mind and body has received particularly limited attention in the study of metabolic disorders, such as diabetes.Type 2 diabetes, the most common form of diabetes, is a chronic disease that affects millions (7). Its symptoms include periodic rises in blood glucose levels (BGLs) because the body produces insufficient insulin and/or resists the effects of insulin, leading to short-term severe shock and multiple long-term complications including strokes, neuropathies, kidney disease, and vision problems (8). Genetic factors appear to be a strong biological trigger (9), and obesity seems to be a powerful environmental trigger (10).Although recognized as relevant psychosocial elements in diabetes management, few psychological factors have been studied for the effect they can exert on diabetic physiology. The majority of studies concerning psychological issues and diabetes have focused on depression, a serious comorbid condition (11), or on the negative effect of distress on disease management (12). Apart from studies on depression and distress, limited efforts have been made to investigate the effect of psychological variables on blood sugar regulation. No studies to our knowledge have investigated the potential for psychological mechanisms to directly influence BGLs.Glucose levels in people with type 2 diabetes follow a particular time course, but how is the course determined? Current models suggest it is determined solely by physiological factors (13). There is, howeve...