Probable MOH was assumed to be the diagnosis when headache frequency was ≥15 d/mo, duration was >4 h, the question "Do you usually take medication to treat your headaches" was answered "yes", and frequency of acute medication use was ≥15 d/mo if the medication was simple analgesics only and ≥10 d/mo if any other (compound analgesics, opioids, triptans and/or ergots).
The trained interviewers asked the participants whether or not they suffered with heartburn or acid regurgitation in the past 12 months, and if yes, the frequency of the symptoms, and the age the symptoms started.
The variables in this block were: nighttime breastfeeding (yes, no), prolonged breastfeeding beyond 12 months (yes, no), and frequency of consumption of sugary snacks between main meals (<3 or ≥3 times/day).
We dichotomized the variable of Chinese herbal medicine use to "no" and "yes" by the frequency of 1 time/month (Table 2).
Hence, GO terms whose value "yes" has a frequency of occurrence smaller than a predefined threshold - the "GO term occurrence threshold" - are removed from the dataset.
The drug use variables included current injecting (yes or no), frequency of injecting, main type of drug injected, time elapsed since start of injecting drug use, frequency of non-injecting drug use and type of drug used mainly as non-injecting drug.
As in previous experiments, an initial exploration of effects due to emotional valence and type of rating on source memory was carried out using hit rates (frequency of "yes" responses for captions that had preceded pictures) and false alarms ("yes" responses to captions that had been followed by imagery).
After physical examination, the participants were asked whether they suffered with heartburn or acid regurgitation in the last 12 months by trained interviewers, and if yes, the severity and frequency of the symptoms were recorded.
Additionally, respondents who reported cooking with a gas stove were also asked "Is there an exhaust fan near this stove that sends fumes outside the home (yes/no)?" Respondents that answered yes were asked about frequency of exhaust fan usage (never, rarely, sometimes, or always) [ 52].
Patient reported behaviour was analysed in terms of a change in their frequency of driving (yes or no) or in terms of changing the use of driving-impairing medicines (yes or no).
