Depression is an important cause of disability in the United States (US). The care experience of major depressive disorder (MDD) is highly variable and has only been documented to a limited degree. This study examines the prevalence incidence and treatment patterns for MDD in the US general population.

In this longitudinal study 2 interview waves were conducted between 2002 and 2015. The initial wave (W1) was carried out with 12,218 individuals from the general population in 8 US states with participants aged 18 years or older. In the second wave (W2) 10,931 of the initial participants agreed to be interviewed again 3 years later; the analyses were carried out for individuals who participated in both interviews (N=10,931). Diagnosis of MDD was confirmed according to Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5) criteria.

The 3-year incidence of MDD was 3.4% (95% CI 3.1%–3.7%). The prevalence of MDD was 5.1% (95% CI 4.7%–5.5%) and 4.2% (95% CI 3.8%–4.6%) in W1 and W2, respectively. The percentages of participants who achieved partial and complete remission were 4.4% (95% CI 4.0%–4.8%) and 3.9% (95% CI 3.5%–4.3%) in W1 compared with 7.9% (95% CI 7.4%–8.4%) and 4.4% (95% CI 4.0%–4.8%) in W2, respectively. The prevalence of MDD was 13.4% and 16.5% in W1 and W2, respectively, when including participants with MDD partial and complete remission episodes. 61.9% of participants with an MDD diagnosis in W1 had at least one associated comorbidity. 41.8% of participants with an MDD diagnosis at W1 still reported significant depressive symptoms at W2. 19.9% of participants in partial remission and 5.5% of participants in complete remission in W1 did not achieve remission in W2. 52.2% and 42.9% of participants with MDD were treated with an antidepressant (AD) in W1 and W2, respectively; selective serotonin reuptake inhibitors (SSRIs) were the most commonly prescribed (34.7% in W1 vs 28.3% in W2). ADs were mainly prescribed by primary care physicians (45.7%) followed by psychiatrists (31.4%), neurologists (2.5%), and other specialties (7.9%). The average duration of treatment was 36.9 (SE 2.4) months. More than one-third of AD users in W1 expressed dissatisfaction with their AD treatment which translated into changes in types of antidepressant in W2.

Depression affects a sizable part of the general population in the US with a prevalence of MDD at 13.4%–16.5%; yet MDD remains largely undertreated as shown by the finding that only about half (52%) of individuals in this study who met the diagnostic criteria for MDD were treated with an antidepressant (SSRI being the most common treatment). In addition, more than a quarter of patients with MDD in this study did not achieve remission after initial treatment underscoring the challenges in successful antidepressant treatment of MDD.

Takeda Pharmaceuticals U.S.A. Inc. and Lundbeck LLC

The complex nature of insomnia and its relationship with organic and mental disorders render diagnosis problematic for epidemiologists and physicians.

A representative UK sample (non-institutionalised, > 14 years old) was interviewed by telephone (n=4972; 79.6% participation rate) with the Sleep-EVAL system. Subjects fell into three groups according to presence of insomnia symptom (s) and/or sleep dissatisfaction.

Insomnia symptoms occurred in 36.2% of subjects. Most of these (75.9%), however, reported no sleep dissatisfaction. In comparison, those also with sleep dissatisfaction had higher prevalence of sleep and mental disorders and longer duration of insomnia symptoms, and were more likely to take sleep-promoting medication, dread bedtime, and complain of light sleep, poor night-time sleep and daytime sleepiness.

Insomnia sufferers differ as to whether they are satisfied or dissatisfied with sleep. Although insomnia symptoms are common in the general population, sleep disturbances among sleep-dissatisfied individuals are more severe. Sleep dissatisfaction seems a better indicator of sleep pathology than insomnia symptoms.

Hypnagogic and hypnopompic hallucinations are common in narcolepsy. However, the prevalence of these phenomena in the general population is uncertain.

A representative community sample of 4972 people in the UK, aged 15–100, was interviewed by telephone (79.6% of those contacted). Interviews were performed by lay interviewers using a computerised system that guided the interviewer through the interview process.

Thirty-seven per cent of the sample reported experiencing hypnagogic hallucinations and 12.5% reported hypnopompic hallucinations. Both types of hallucinations were significantly more common among subjects with symptoms of insomnia, excessive daytime sleepiness or mental disorders. According to this study, the prevalence of narcolepsy in the UK is 0.04%.

Hypnagogic and hypnopompic hallucinations were much more common than expected, with a prevalence that far exceeds that which can be explained by the association with narcolepsy. Hypnopompic hallucinations may be a better indicator of narcolepsy than hypnagogic hallucinations in subjects reporting excessive daytime sleepiness.