Hemorrhoids occur when an increase of pressure in the veins around the anus and rectum causes these veins to swell and enlarge. There are numerous possible causes of this increased pressure, including:

• Straining during bowel movements. Often considered the most common cause of hemorrhoids. This frequently occurs in patients with chronic constipation. Although this straining is known to irritate existing hemorrhoids, some scientists believe that is does not directly contribute to the development of new hemorrhoids.
  
  
• Long periods of time on the toilet. Sitting on the toilet for a long time causes increased pressure on the veins in the anal canal.
  
  
• Pregnancy and childbirth. A developing fetus places a lot of pressure on the rectal area. Hormonal changes during pregnancy may cause the veins around the anus and rectum to swell. The act of childbirth also places severe pressure on the veins in this area.
  
  
• Frequent heavy lifting. Lifting heavy objects can cause strain similar to that caused by constipation. Much like straining during bowel movements, frequent heavy lifting is known to make hemorrhoids worse and is often thought to contribute to their formation. However, some scientists do not believe this contribution is a direct link.
  
  
• Sitting or standing for too long. Sitting down or standing for extended periods of time increases the pressure in the anal and rectal veins. This may lead to hemorrhoids and worsens hemorrhoids that already exist.
  
  
• Other possible causes include:
  
• • Obesity
  • Chronic cough
  • Chronic diarrhea
  • Liver disease
  • Overuse of laxatives or enemas

Hemorrhoids are more likely to develop as a patient ages. Most people develop them after the age of 30. Patients who have family members with hemorrhoids are also more likely to develop hemorrhoids at some point in their life. This is believed to be due to an inherited tendency for hemorrhoid formation, meaning that the patient is more susceptible than other patients to the factors that cause hemorrhoids.