Approach
The diagnosis of seasonal affective disorder (SAD) is based primarily on:
A self-reported patient history
A careful assessment of atypical mood symptoms
A period of at least 2 years of reliable seasonal mood changes.
Obtaining collateral information from family members or friends may provide additional information for establishing temporal mood changes and the degree of impairment. Objective findings, based on physical examination and laboratory testing, tend to be within normal limits.[15] However, certain medical, substance-use, and other psychiatric conditions associated with mood changes, sleep disruptions, and fatigue should be ruled out.
Seasonal history
History includes assessing risk factors for the condition. Risk factors that are strongly associated with SAD include female sex, an age of onset of 20 to 30 years, positive family history of the condition, and living in latitudinal areas that are exposed to diminished light during winter and increased light during summer.
All patients must meet the diagnostic criteria for either a recurrent major depressive disorder or a bipolar mood disorder. A seasonal sub-specifier may then be applied if the following additional criteria are met.[39]
A regular temporal relationship exists between the onset of mood symptoms and a particular time of year that is not better accounted for by seasonally related psychosocial stressors (e.g., seasonal unemployment, bereavement, trauma).
Full remission of mood symptoms (or change from depression to hypomanic/manic symptoms) occurs at a regular time of year (e.g., resolution of depressive symptoms during the spring).
Over the last 2 years, at least 2 major depressive episodes have occurred that demonstrate the temporal seasonal pattern without evidence of non-seasonal major depressive episodes occurring during that same time period.
Over the lifetime course, the number of seasonal major depressive episodes substantially outnumbers non-seasonal major depressive episodes.
The current severity of SAD may also be further documented according to the number of criterion symptoms present, the severity of those symptoms, and the degree of functional impairment associated with the condition:[39]
Mild: enough symptoms present to meet diagnostic criteria, distressing but manageable symptoms, with minor impairment in social or occupational functioning.
Moderate: increased number of symptoms beyond those required for the diagnosis, more intense symptomatic presentation causing increased impairments in social or occupational functioning.
Severe: number of symptoms substantially in excess of those required for the diagnosis, symptoms are seriously distressing and result in substantial impairment in social and occupational functioning.
SAD may be further specified as being either in partial remission (i.e., symptoms from last seasonal episode are still present, yet full diagnostic criteria are not met, or full remission of symptoms for a sustained period lasting less than 2 months) or full remission (i.e., no significant symptoms present for at least 2 months).
Sub-syndromal SAD is characterised by seasonal mood disruptions with milder functional impairments. Symptom changes may not be as severe. Patients may not meet the diagnostic criteria for a clinical mood disorder. However, the mood disruption and impairments may still be significant.[39][40]
Most commonly, patients with SAD have autumn- or winter-onset depression, with symptoms remitting during the spring or summer. Less common presentations include onset of depressive symptoms during the summer months, and/or hypomanic or manic symptoms during the winter months. Within bipolar disorders, a seasonal pattern may be more common among people with bipolar II disorder compared with those with bipolar I disorder.
Symptoms
Patients generally report common depressive symptoms, such as:[41]
Sad mood
Restricted affect
Loss of interest
Poor energy
Psychomotor agitation or retardation
Feelings of hopelessness, helplessness, worthlessness, or inappropriate guilt
Concentration difficulties
Indecisiveness
Thoughts of suicide
Patients may also report a variety of somatic symptoms, including vague pain complaints, which may precipitate their engagement in primary care.[25][42] Autumn- or winter-onset SAD may additionally involve a variety of atypical depressive symptoms, such as:[43]
Hypersomnia
Hyperphagia with carbohydrate cravings
Weight gain
Slowed movement
Heaviness in the limbs (leaden paralysis)
Emotional symptoms may also include irritability and anger.[44] Spring-onset depressive symptoms tend to be characterised by more common typical vegetative depressive symptoms. Although less common than autumn- or winter-onset SAD, manic or hypomanic episodes may occur during the spring and summer months. Manic symptoms include at least a 1-week-long, distinct period of:[39]
Abnormally and persistently elevated, expansive or irritable mood
Abnormally and persistently increased activity or energy
Inflated self-esteem and grandiosity
Decreased need for sleep
Pressured speech or increased frequency of talking
Racing thoughts
Distractibility
Increased goal-directed activity or psychomotor agitation
Excessive engagement in pleasurable activities with a high degree of risk (e.g., spending, sexual activity)
Hypomanic symptoms tend to be less intense than manic episodes, and must occupy a distinct period lasting for at least 4 days. Seasonal changes in mood may also be associated with alcohol-use disorders.[14][36] Increased alcohol use may develop to regulate negative affect and should be routinely assessed in the clinical setting. Functional impairments in personal, social, and occupational domains are common, as withdrawal, isolation, and inactivity tend to compound problems and increase the burden of symptom management. Interview questions should assess for seasonal changes in alcohol use among all patients.
Screening and assessment tools
First-line screening for clinical depression can be done in an efficient manner with the Patient Health Questionnaire-9 (PHQ-9).[45] Subsequent follow-up questions assess a seasonally dependent, temporal pattern. The Seasonal Health Questionnaire (SHQ) may also be used and is a more sensitive and specific self-report measure of SAD.[46] The Seasonal Pattern Assessment Questionnaire (SPAQ) is another commonly used instrument that may be beneficial as a general index of severity and functional impairment.[47][48] Assessment of mood and associated impairments can be further augmented by self-report measures and interviews with family members or friends.
Physical examination
There are typically no objective findings from the physical examination. Patients may present with pain-related complaints and other vague somatic symptoms. Weight gain during the autumn or winter months may be observed due to the combination of hyperphagia and physical inactivity. Slowed movements and fatigue may also be observed.
Manic or hypomanic symptoms, more commonly observed in spring or summer, may be associated with heightened sympathetic nervous system activity (e.g., tachycardia, increased systolic blood pressure, restlessness). Furthermore, healthcare providers should assess for current drug and substance use (e.g., alcohol, nicotine, stimulants, benzodiazepines, opioids), as the effects of these substances can either mask or amplify SAD symptoms and could negatively affect treatment response.
Investigations
Self-report, clinical interview, collateral information, and behavioural observation are sufficient for screening and to establish a diagnosis. Laboratory testing or imaging studies are not typically indicated for SAD. For severe clinical presentations, providers may consider a routine blood metabolic panel with thyroid-stimulating hormone levels to rule out contributing biological factors (e.g., hypothyroidism). Toxicology screening may be indicated to determine whether alcohol or illicit substances are contributing to the clinical presentation.
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