Most people who suffer from constipation manage a type known as functional or idiopathic constipation. This type of constipation is so called because the underlying cause is not identifiable, yet the condition can be easy diagnosed due to the symptoms. Treatment at first consists of increased dietary fiber. If this is ineffective, patients are recommended to try a laxative.
Generally the opinion among the scientist and researcher population is that using laxative constipation treatments properly is safe. But as constipation is occasionally a chronic condition that necessitates use of laxatives over long periods, suspicions about unintended side-effects and health issues have arisen. One problem is the development of myths regarding this line of medication.
There are three kinds of misconceptions about laxative usage. The first is the idea that long term use causes nerves in the gastrointestinal tract to be damaged. The second is the idea that long term use leads to higher chance of cancer. The third is that the gut starts to become "immune" to laxatives and perhaps suffer "rebound" effects that worsen constipation.
On the topic of the first misconception, reports about nerve damage came up first in a survey of patients who were using laxative constipation treatments. Colonoscopy showed discoloration in their intestinal lining, and some were diagnosed with damage to the nerves. But the correlative link was never made definitive. Many criticized the findings by pointing out in general patients with constipation had more chance of nerve damage, regardless of laxative use or not.
On the topic of the second, people reported a connection from laxatives to cancer by looking at animal experimentation. Rodents which were given very high doses of laxatives showed more DNA damage and thus propensity toward cancer. Yet the studies used extremely high concentrations of drugs that are never seen in humans. Likewise, studies with such high concentrations of aspartame and artificial sweeteners show a link between consumption and cancer that are rarely realized in epidemiological surveys.
Regarding the third, it seems that anecdotes from patients who were seeing decreased efficacy gave rise to the belief of laxative intolerance. However, studies both in rats and in paraplegic patients who had been on laxatives for as long as 34 years showed that the efficacy of laxatives remained more or less undiminished over these long times.
Laxatives seem to be a helpful part of the treatment regimen to combat constipation. The reports of these three kinds of side effects needs to evaluated against case studies which show the opposite: that long term side-effects are not a given.