Purpose: Medication non-adherence is widely reported, but little is known about how multiple illnesses affect patients' decisions around adherence. This study explored this decision-making process to identify whether, and how, people “trade” between medicines or diseases.

Method: Twenty insured community-dwelling seniors were interviewed. Interviewees were selected by gender; income; >3 medicines and >2 morbidities. In-depth qualitative interviews covered: knowledge and beliefs about the disease and medicines; influence of prescribers, “the system”, media and family; and “trading” behavior.

Results:12 women and 8 men were interviewed, age range: 67-90, taking 4-12 drugs, with 3-9 co-morbidities. People reported trading between medicines for different diseases (eg: glaucoma before hypertension); medicines for the same disease (eg: rejecting a third inhaler) and between medicines and non-medicine health-related behavior (eg: using diet to control diabetes). All interviewees had made at least one trading decision in the past leading to adjusting dosing, swapping, or stopping a medicine. Most would consider trading one of their medicines over another in the future. There was general resistance to taking medicines, with minimal medicines-taking preferred, particularly with mental health medicines.

The most common motivators to trade between medicines were symptom control, previous experience, fear about the future (affective forecasting), side effects, beliefs about the illness and cost of medicines. Interviewees used one or more motivators to trade between medicines or diseases. Decision-making based on one motivator (single-attribute or “experiential”) was much more common than decisions using multiple motivators (multiple-attribute or “rational”). There was no dominant disease, medicine or motivator to trade. Also, where individuals reported more than one trading decision, they did not use the same motivator for all trading decisions.

Both single- and multiple-attribute decision-making could result in acceptance, modification or rejection of a medicine, but the decision-making process was very different. One person could passively accept, actively accept, actively modify and reject different medicines within their regimen, using different motivators for each decision.

Conclusions: Community-dwelling seniors with multiple morbidities trade between medicines and use many decision mechanisms during trading. Specific decisions are generally driven by one motivator. Within one individual, adherence to one medicine does not predict adherence to other medicines and motivation to adhere is different for different medicines. These results have implications for methods that assume multi-attribute decision-making around medicines.