A 41-year-old female with treatment-resistant depression and generalized anxiety disorder presents with persistent insomnia despite adequate doses of her antidepressant. She reports difficulty initiating sleep, averaging 45 minutes to fall asleep, and waking 3-4 times nightly. She also reports that her bed partner has observed loud snoring and witnessed episodes where she appears to stop breathing during sleep. Her BMI is 34.2 kg/m2, and she reports excessive daytime sleepiness with an Epworth Sleepiness Scale score of 16. She attributes her fatigue entirely to depression and has been requesting an increase in her antidepressant or addition of a sedative-hypnotic. Which assessment consideration is most important before attributing her sleep disturbance solely to her psychiatric conditions?