Dietary factors such as spice consumption, were hypothesized to cause ulcers until late in the 20th century, but have been shown to be of relatively minor importance. Caffeine and coffee, also commonly thought to cause or exacerbate ulcers, appear to have little effect. Similarly, while studies have found that alcohol consumption increases risk when associated with "H. pylori" infection, it does not seem to independently increase risk. Even when coupled with "H. pylori" infection, the increase is modest in comparison to the primary risk factor.

Stress due to serious health problems such as those requiring treatment in an intensive care unit is well described as a cause of peptic ulcers, which are termed stress ulcers.

While chronic life stress was once believed to be the main cause of ulcers, this is no longer the case. It is, however, still occasionally believed to play a role. This may be by increasing the risk in those with other causes such as "H. pylori" or NSAID use.

Smoking has been linked to a variety of disorders of the stomach. Tobacco is known to stimulate acid production and impairs production of the protective mucus. This leads to development of ulcers in the majority of smokers.

Chronic stomach problems have also been linked to excess intake of alcohol. It has been shown that alcohol intake can cause stomach ulcer, gastritis and even stomach cancer. Thus, avoidance of smoking and excess alcohol consumption can help prevent the majority of chronic stomach disorders.

One of the most causes of chronic stomach problems is use of medications. Use of aspirin and other non-steroidal anti-inflammatory drugs to treat various pain disorders can damage lining of the stomach and cause ulcers. Other medications like narcotics can interfere with stomach emptying and cause bloating, nausea, or vomiting.

The majority of chronic stomach problems are treated medically. However, there is evidence that a change in life style may help. Even though there is no specific food responsible for causing chronic stomach problems, experts recommend eating a healthy diet which consists of fruits and vegetables. Lean meat should be limited. Moreover, people should keep a diary of foods that cause problems and avoid them.

The average age of onset is 40 to 60 years, and men are affected more often than women. Adults with Ménétrier disease have a higher risk of developing gastric adenocarcinoma.

Horses may develop pharyngitis, laryngitis, or esophagitis secondary to indwelling nasogastric tube. Other complications include thrombophlebitis, laminitis (which subsequently reduces survival rate), and weight loss. Horses are also at increased risk of hepatic injury.

Survival rates for DPJ are 25–94%. Horses that survive the incident rarely have reoccurrence.

Cancers of the stomach are rare and the incidence has been declining worldwide. Stomach cancers usually occur due to fluctuations in acidity level and may present with vague symptoms of abdominal fullness, weight loss and pain. The actual cause of stomach cancer is not known but has been linked to infection with "Helicobacter pylori", pernicious anemia, Menetriere's disease, and nitrogenous preservatives in food.

Evidence does not support a role for specific foods including spicy foods and coffee in the development of peptic ulcers. People are usually advised to avoid foods that bother them.

Transient gastroparesis may arise in acute illness of any kind, as a consequence of certain cancer treatments or other drugs which affect digestive action, or due to abnormal eating patterns.

It is frequently caused by autonomic neuropathy. This may occur in people with type 1 or type 2 diabetes. In fact, diabetes mellitus has been named as the most common cause of gastroparesis, as high levels of blood glucose may effect chemical changes in the nerves. The vagus nerve becomes damaged by years of high blood glucose or insufficient transport of glucose into cells resulting in gastroparesis. Gastroparesis has also been associated with connective tissue diseases such as scleroderma and Ehlers–Danlos syndrome, and neurological conditions such as Parkinson's disease. It may also occur as part of a mitochondrial disease. Opioids and anticholinergic medications can cause medication-induced gastroparesis.

Chronic gastroparesis can be caused by other types of damage to the vagus nerve, such as abdominal surgery. Heavy cigarette smoking is also a plausible cause since smoking causes damage to the stomach lining.

Idiopathic gastroparesis (gastroparesis with no known cause) accounts for a third of all chronic cases; it is thought that many of these cases are due to an autoimmune response triggered by an acute viral infection. Gastroenteritis, mononucleosis, and other ailments have been anecdotally linked to the onset of the condition, but no systematic study has proven a link.

Gastroparesis sufferers are disproportionately female. One possible explanation for this finding is that women have an inherently slower stomach emptying time than men. A hormonal link has been suggested, as gastroparesis symptoms tend to worsen the week before menstruation when progesterone levels are highest. Neither theory has been proven definitively.

Gastroparesis can also be connected to hypochlorhydria and be caused by chloride, sodium and/or zinc deficiency, as these minerals are needed for the stomach to produce adequate levels of gastric acid (HCl) in order to properly empty itself of a meal.

Gastritis may also develop after major surgery or traumatic injury ("Cushing ulcer"), burns ("Curling ulcer"), or severe infections. Gastritis may also occur in those who have had weight loss surgery resulting in the banding or reconstruction of the digestive tract.

The causes are divided into benign or malignant.

- Benign

- Peptic ulcer disease

- Infections, such as tuberculosis; and infiltrative diseases, such as amyloidosis.

- A rare cause of gastric outlet obstruction is blockage with a gallstone, also termed "Bouveret's syndrome".

- In children congenital pyloric stenosis / congenital hypertrophic pyloric stenosis may be a cause.

- A pancreatic pseudocyst can cause gastric compression.

- Pyloric mucosal diaphragm could be a rare cause.

- Malignant

- Tumours of the stomach, including adenocarcinoma (and its linitis plastica variant), lymphoma, and gastrointestinal stromal tumours

As a general rule, GDV is of greatest risk to deep-chested dogs. The five breeds at greatest risk are Great Danes, Weimaraners, St. Bernards, Gordon Setters, and Irish Setters. In fact, the lifetime risk for a Great Dane to develop GDV has been estimated to be close to 37 percent. Standard Poodles are also at risk for this health problem, as are Irish Wolfhound, Doberman Pinschers, Rottweilers, German Shorthaired Pointer, German Shepherds, Rhodesian Ridgebacks. Basset Hounds and Dachshunds have the greatest risk for dogs less than .

Megaduodenum is a congenital or acquired dilation and elongation of the duodenum with hypertrophy of all layers that presents as a feeling of gastric fullness, abdominal pain, belching, heartburn, and nausea with vomiting sometimes of food eaten 24 hours prior.

Immediate treatment is the most important factor in a favorable prognosis. A delay in treatment greater than six hours or the presence of peritonitis, sepsis, hypotension, or disseminated intravascular coagulation are negative prognostic indicators.

Historically, GDV has held a guarded prognosis. Although "early studies showed mortality rates between 33% and 68% for dogs with GDV," studies from 2007 to 2012 "reported mortality rates between 10% and 26.8%". Mortality rates approach 10% to 40% even with treatment. A study determined that with prompt treatment and good preoperative stabilization of the patient, mortality is significantly lessened to 10% overall (in a referral setting). Negative prognostic indicators following surgical intervention include postoperative cardiac arrhythmia, splenectomy, or splenectomy with partial gastric resection. Interestingly, a longer time from presentation to surgery was associated with a lower mortality, presumably because these dogs had received more complete preoperative fluid resuscitation and were thus better cardiovascularly stabilized prior to the procedure.

In a peptic ulcer it is believed to be a result of edema and scarring of the ulcer, followed by healing and fibrosis, which leads to obstruction of the gastroduodenal junction (usually an ulcer in the first part of the duodenum).

The cause of Ménétrier disease is unknown, but it has been associated with HCMV infection in children and "H. pylori "infections in adults. Additionally, increased TGF-α has been noted in the gastric mucosa of patients with the disease.

The median age at diagnosis is 38 years. Women are at higher risk for developing breast cancer.

The condition most commonly affects people between the ages of 30 and 60. The prevalence in unknown, but estimated to be about 1 per 100,000 people.

Gastric atresia is the complete occlusion of the pyloric outlet of the stomach and is an extremely rare event.

Little is known on the prognosis of achlorhydria, although there have been reports of an increased risk of gastric cancer.

A 2007 review article noted that non-"Helicobacter" bacterial species can be cultured from achlorhydric (pH > 4.0) stomachs, whereas normal stomach pH only permits the growth of "Helicobacter" species. Bacterial overgrowth may cause false positive H. Pylori test results due to the change in pH from urease activity.

Small bowel bacterial overgrowth is a chronic condition. Retreatment may be necessary once every 1–6 months. Prudent use of antibacterials now calls for an antibacterial stewardship policy to manage antibiotic resistance.

Zollinger–Ellison syndrome (ZES) is a disease in which tumors cause the stomach to produce too much acid, resulting in peptic ulcers. Symptoms include abdominal pain and diarrhea.

The syndrome is caused by a gastrinoma, a neuroendocrine tumor that secretes a hormone called gastrin. The tumor causes excessive production of gastric acid, which leads to the growth of gastric mucosa and proliferation of parietal and ECL cells.

ZES may occur on its own or as part of an autosomal dominant syndrome called multiple endocrine neoplasia type 1 (MEN 1). The primary tumor is usually located in the pancreas, duodenum or abdominal lymph nodes, but ectopic locations (e.g., heart, ovary, gallbladder, liver, and kidney) have also been described.

Smoking increases the risk of developing gastric cancer significantly, from 40% increased risk for current smokers to 82% increase for heavy smokers. Gastric cancers due to smoking mostly occur in the upper part of the stomach near the esophagus. Some studies show increased risk with alcohol consumption as well.

Primary complications of gastroparesis include:

- Fluctuations in blood glucose due to unpredictable digestion times (in diabetic patients)

- General malnutrition due to the symptoms of the disease (which frequently include vomiting and reduced appetite) as well as the dietary changes necessary to manage it

- Severe fatigue and weight loss due to calorie deficit

- Intestinal obstruction due to the formation of bezoars (solid masses of undigested food)

- Bacterial infection due to overgrowth in undigested food

Most damage to the pyloric valve occurs as a complication of gastric surgery. Other causes of biliary reflux may be:

- Peptic ulcer

- Gallbladder surgery (cholecystectomy)

A significant fraction of cases are idiopathic, with no identified specific etiology.

Dumping syndrome occurs when food, especially sugar, moves too fast from the stomach to the duodenum—the first part of the small intestine—in the upper gastrointestinal (GI) tract. This condition is also called rapid gastric emptying. It is mostly associated with conditions following gastric or esophageal surgery, though it can also arise secondary to diabetes or to the use of certain medications; it is caused by an absent or insufficiently functioning pyloric sphincter, the valve between the stomach and the duodenum.

Dumping syndrome has two forms, based on when symptoms occur. Early dumping syndrome occurs 10 to 30 minutes after a meal. It results from rapid movement of fluid into the intestine following a sudden addition of a large amount of food from the stomach. The small intestine expands rapidly due to the presence of hypertonic/hyperosmolar contents from the stomach, especially sweet foods. This causes symptoms due to the shift of fluid into the intestinal lumen, with plasma volume contraction and acute intestinal distention. Osmotic diarrhea, distension of the small bowel leading to crampy abdominal pain, and reduced blood volume can result.

Late dumping syndrome occurs 2 to 3 hours after a meal. It results from excessive movement of sugar into the intestine, which raises the body's blood glucose level and causes the pancreas to increase its release of the hormone insulin. The increased release of insulin causes a rapid drop in blood glucose levels, a condition known as alimentary hypoglycemia, or low blood sugar.

DPJ is most commonly seen in the Southeastern US, although cases have been reported throughout the United States and Canada, as well as sporadically in the United Kingdom and Europe. Horses in the Southeastern US tend to have a more severe form of the disease relative to other locations. Age, breed, and gender appear to have no effect on disease prevalence.