Chalder Fatigue Scale

The Chalder Fatigue Scale (CFS) is a validated clinical instrument designed to assess the presence and severity of fatigue. Originally developed for research in chronic fatigue syndrome, it has since become a standard measure in broad clinical practice to evaluate fatigue across various physical and mental health conditions. By capturing symptoms over the past month, it provides clinicians with a reliable, standardized baseline that subjective reporting alone may miss. It is especially useful when differentiating exhaustion from underlying depression or assessing the overall somatic burden.

The scale distinguishes between two core dimensions of the fatigue experience: physical exhaustion (such as lack of energy and muscle weakness) and cognitive fatigue (such as concentration difficulties and word-finding problems). This dimensional approach helps clinicians better understand the functional impact of a patient's fatigue, tailor their psychoeducation, and accurately track changes over the course of treatment or rehabilitation.

The CFS evaluates the severity of recent fatigue across two distinct clinical dimensions:

• Physical fatigue: Assesses somatic manifestations such as subjective tiredness, increased need for rest, feeling sleepy, loss of muscle strength, and difficulty initiating activities, which may impact a patient's capacity to engage in exercise for mental health.
• Mental fatigue: Captures cognitive manifestations, including difficulties with concentration, memory, clear thinking, and verbal fluency (such as making slips of the tongue).

The instrument is designed for adults presenting with unexplained fatigue, suspected chronic fatigue syndrome, or fatigue secondary to other medical conditions, and can be relevant when formulating a cognitive behavioral model of insomnia.

Clinicians typically administer the CFS when a patient reports persistent exhaustion, to structure the assessment and monitor the impact of fatigue on daily functioning.

• Intake baseline: To establish a standardized measure of both physical and mental fatigue at the beginning of care, helping to contextualize how the body responds to stress.
• Monitoring change: To track fluctuations in fatigue severity over time, particularly when introducing pacing strategies or building a healthy habit plan.
• Differential support: To clarify whether the patient's fatigue is primarily physical (somatic exhaustion) or mental (cognitive fog), providing useful data when evaluating coping strategies across different symptom profiles.
• Screening: To identify cases of severe clinical fatigue that may warrant further medical investigation or specialized support.

Using a validated score allows the clinician to quantify the subjective experience of fatigue and track objective progress beyond general clinical impressions.