There’s lots of discussion among researchers about which scale best allows people to report on symptoms or opinions.
The consensus: whereas an even numbered scale forces people to err on the side or a positive or negative opinion (in a 1-6 scale, 3 is slightly negative and 4 is slightly positive), an odd-numbered scale allows for a “neutral” choice. So in a seven point scale 4 means neutral, neither bad or good.
Five and seven point scales are commonly used in research because too many rating options can create confusion. It’s tough enough evaluating symptoms and making comparisons about symptom severity from day to day! We opted for a seven point because it allows for 50% more nuance and granularity than a five point scale.