Obesity has become one of the most severe global public health problems of the 21^st century—more than 35% of men and 40% of women with obesity in the United States (1, 2). Obesity may be associated with social stigma and self-potential shame, causing a psychological burden on patients with obesity and may increase with body mass index (BMI) (3). There has been growing evidence of a two-way association between mental illness and obesity, particularly among bariatric surgery candidates (4). Depression and anxiety are common mood disorders that often coexist with obesity (5). In the general United States population, the prevalence of depression in patients with obesity seeking surgery exceeds the published prevalence (19% VS 8%) (5). Depression has long been thought to be significantly associated with binge-eating disorders (BED) (6). Eating disorder is associated with an additional burden on patients with obesity, Such as low quality of life, impulsivity, and emotional regulation disorders (7), in the regulation of hunger/satiety (8), on the palate (9), on food preferences or intolerances (10, 11), and a higher likelihood of coexisting mental health conditions.

Although bariatric surgery has been shown to alleviate complications related to physical health, its effects on mental illness have not been clearly articulated (12). In the United States, the rate of bariatric surgery remains < 1% among the eligible population (13). This low rate may be due to questions about the long-term effectiveness of bariatric surgery (14). Bariatric surgery was associated with significant improvements in depression, BED (15, 16), and eating disorders (17). While the results were encouraging, with long-term follow-up data suggesting that some postoperative patients did not experience psychological benefits or reported increased rates of depression and BED recurrence (16, 18). People are concerned about the potential risks of mental health disorders after bariatric surgery, including self-harm, suicide, and substance abuse (19, 20). One study reported that patients after bariatric surgery had a 1.98-fold increased risk of suicide compared to usual care of patients with obesity (21). The incidence of suicide and suicide attempts occurs on average 3.8 to 3.9 years after surgery (22). In addition, the incidence of self-harm and alcohol use disorders (AUD) increases postoperatively (23, 24) and may be associated with changes in reward mechanisms after bariatric surgery (25). we re-evaluate the meta-analysis/systematic review of all the mental health outcomes of bariatric surgery to reveal the quality and strength of the evidence.

This umbrella review summarised the highest-level evidence on bariatric surgery for multiple mental health outcomes. We included nine meta-analyses/systemic reviews assessing 20 different mental health outcomes. This study found that bariatric surgery was beneficial to improving overall mental health, reducing depression and anxiety symptoms in patients with obesity, and eating disorders (e.g., BED) also improved after surgery. In addition, bariatric surgery can increase the risk of suicide, self-harm, and increased AUD after surgery. Although the mental state has improved after the operation, the mechanism behind this evidence is still unclear. It may not be bariatric surgery itself, but the life changes caused by weight loss (caused by bariatric surgery). The same is true of harmful consequences.

Bariatric surgery can significantly improve the symptoms of depression and anxiety and reduce the incidence; this has been proved in many meta-analyses (35, 36, 38, 39).

As expected, The degree of change in depressive symptoms is related to the shift in BMI after the operation (43). Although bariatric surgery can improve depressive symptoms in the short term, long-term follow-up studies show that the Hospital anxiety and depression scale is equivalent to before surgery in four years and nine years after bariatric surgery (44, 45). There may be several paths in its mechanism. (a) First, body image satisfaction, self-worth, interpersonal relationships (5), and an increase in physical activity can be improved after the operation (46, 47). Secondly, after surgery, changes in digestion or intestinal absorption may change biochemical signals in the brain; for example, changes in intestinal microflora, intestinal peptides (including ghrelin, glucagon-like peptide 1, peptide YY and cholecystokinin) are related to depression and anxiety, and bile acids can have a central impact on the emotional and behavioural responses caused by cocaine (48). Third, patients whose depression is likely to improve on their own are more likely to undergo surgery. Notably, studies have reported an 8% to 74% reduction in the prevalence of postoperative depression (5). However, the prevalence of postoperative depression is still as high as 15.3%, of which mild depression accounts for 64.9% (37); that may be related to weight regain following bariatric surgery, eating disorders, and impaired quality of life.

There was a significant improvement in BED (49, 50) after bariatric surgery, especially in the first 12 months after surgery, and larger effect sizes were found. One study included seven studies that reported the prevalence of eating disorders as 7.83% (17). Even if the postoperative prevalence is less than 10%, the disease can significantly affect prognosis and BMI reduction. Among them, the prevalence of BED is 3.81% (17). After bariatric surgery, avoiding high-fat/high-sugar foods may be a learned response to postprandial discomfort or dumping syndrome (51), this in turn helps to control obesity in this population (52). With longer postoperative follow-ups, conflicting outcomes emerged. Smith et al. (53) reported that BED increased from 2.1% to 4% after seven years, and loss of control eating increased from 24.6% to 26.4%. Conversely, Kalarchian et al. (54) report that the prevalence of eating disorders drops to 0% within seven years. The reason may be that preoperative comprehensive nutrition and psychological behaviour evaluation, education, and support decreased with time (55).

Notably, bariatric surgery is associated with an increased risk of suicide, self-harm, and AUD (40, 42). The prevalence of suicide after bariatric surgery was 0.3% (41). Peterhansel et al. (19) who reviewed suicide after bariatric surgery, reported that suicide rates were estimated at 4.1 per 10,000 people per year, with above-average suicide rates in bariatric surgery patients. Lack of improvement in quality of life after surgery, persistent or recurrent sexual dysfunction and interpersonal problems, and limited physical activity can all lead to an increased risk of suicide (20). The degree of BMI reduction does not seem to explain the change in mental distress after bariatric surgery (56). Compared with other patients undergoing surgery, the patients who have committed suicide or attempted suicide have similar or more significant BMI reduction (57). People with pre-existing mental illnesses such as depression and eating disorders are more likely to commit suicide after surgery due to the underlying psychiatric effects of people with obesity (58). The surgery itself increases potential postoperative problems, such as difficulty controlling pain leading to substance abuse, complications requiring further treatment, dissatisfaction with BMI reduction, excess skin, and scarring (59–61). Neuroendocrine changes and nutritional deficiency caused by postoperative malabsorption and/or irregular eating behaviour may also increase the risk of suicide (62). Because of the potential symptom change after the operation (cross-addiction hypothesis: from overeating to excessive drinking), it may be related to depressive symptoms and suicide attempts, which leads to an increase in the risk of AUD (63, 64). Bariatric surgery is associated with a significant increase in moderate to high-risk AUD (42). One study reported an 8% incidence of postoperative alcohol use/abuse; patients were more likely to drink heavily after surgery than before surgery, 19% had significant alcohol consumption before bariatric surgery, and 23% had apparent alcoholism after bariatric surgery (65). Of the three studies that reported rates of alcohol abuse (23, 66, 67), two studies reported an increase in alcohol problems after RYGB (23, 67), another study reported that no alcohol problems were found in LAGB (66). Increased alcohol consumption after RYGB may be due to physiological changes after gut bypass that are absent after LAGB (including increased release of glucagon-like peptide 1 and peptide YY after meals and decreased circulating acyl-ghrelin) (68, 69); these changes contribute to changes in neural activity (70). Intestinal flora may affect mood and behaviour, and exposure to abused drugs, such as alcohol and opioids, will induce intestinal microbial ecological imbalance (48).

In addition, we found no evidence to support a link between personality disorders and PTSD and changes in BMI reduction outcomes. Depression and anxiety are common among candidates for bariatric surgery. About 40% of patients with obesity have underlying psychiatric disorders, and early identification and optimisation of these disorders are important because they can affect surgical outcomes (71). In the future, we still need to pay attention to the mental health of patients with obesity and assess their mental health status before and after surgery.

We found that bariatric surgery effectively improved mental health and most mental health-related outcomes, such as anxiety symptoms, depression symptoms, eating disorders, and BED. However, these should be cautiously approached after bariatric surgery due to the increased risk of unfavourable mental suicide, self-harm, and AUD.

SL: Conceptualization, Data curation, Formal Analysis, Methodology, Project administration, Software, Writing – original draft, Writing – review & editing. SD: Data curation, Investigation, Methodology, Software, Supervision, Writing – original draft. FZ: Data curation, Investigation, Methodology, Software, Validation, Writing – original draft. DZ: Conceptualization, Data curation, Formal Analysis, Investigation, Methodology, Project administration, Writing – review & editing. CW: Formal Analysis, Methodology, Project administration, Supervision, Validation, Writing – review & editing. ZD: Conceptualization, Data curation, Formal Analysis, Project administration, Resources, Supervision, Writing – review & editing.