Medication non-compliance is a huge issue in public health because not taking medications means that people do not maintain health, they risk more serious health problems, and they complicate the health concerns that their medications are meant to treat. Infections resistant to antibiotics is a prime example of the public health implications of failure to adhere to medication regimens as prescribed.
Aside from the common issue of not having money to buy medications and thus take them as prescribed there are four simple reasons that doctors (and friends and family) tend to ignore, downplay or dismiss:
1. Noone wants to take medication. We do not want to admit that we are sick or that we are dependent on a medication in order to feel better. This is particularly true for chronic conditions that we have for a lifetime and for those that carry stigma, like mental illness. Every now and again we want to take a 'med break' to see if we have gotten better or if we really 'need' to take those drugs
2. Side effects are often as problematic as the drugs themselves. One of the main side effects which can be problematic for a lot of people is weight gain. Noone wants to get fat if they don't have to, and making it seem that it's better for me to be sane and fat than a little (or maybe not so little) crazy and not so fat, is not a good argument in a society yearning to be thin. Neither is the risk to kidneys and liver seem to be worth the sane brain. Throw in the quarterly blood tests that monitor organ function as a result of taking these drugs and the motivation to take them suddenly goes out the window. If someone needs to take medications for a side effect, their motivation to take the first medication can decrease.
3. Sometimes we forget. The reasons for this can be as simple as sleeping at a friend's house and not bringing along a night's worth of meds to complicated medication routines that make a regular routine a challenge. Take without food this one and take with food that one. Take this one 4 times a day and the other one 3 times a day and the other one at night and the other in the morning. Who's got time for all that.
4. We don't understand what the drugs do and therefore are not motivated to take them. Let's acknowledge that a lot of medications work but doctors do not often know why. That said, a patient who knows why they are taking a drug, how it works and why they need to take it is much more likely to take their medication than someone who was handed a prescription to fill, suffers some side effects and wonders what it is the drug is supposed to do.
So what to do when we have to take medications for whatever conditions it is (from hypertension to diabetes to schizophrenia to allergies) that ails us? Well first, perhaps there can be more combination medications for an illness in the manner of HIV/AIDS where pill burden became such an issue that combination drugs became standard. Where are the combination drugs for mental health or lupus or....? Doctors need to work more closely with their clients to educated them about their medications and to find ways to mediate the side effects and complicated drug regimens. Perhaps if they take a more holistic approach then medications for some illnesses can be lessened if clients do more lifestyle changes and promote those changes instead of making drugs the key feature of treatment.
Lastly, although I chose to ignore cost, it should be clearly understood that if medications in the USA were cheaper like they are in countries with single payer healthcare systems (due to economies of scale that help in the negotiation of lower prices), then perhaps adherence would be less of an issue.