The Clinical Global Impression (GLI) is a scale a doctor can use when evaluating the severity of mental illness in a patient and the patient's response to treatment. It can provide a useful framework for a quick assessment and is usually noted in a patient's chart to provide a record of information about the patient's progress in evaluation and therapy. It is important to be aware that this is a subjective scale based on observation, interview, and the clinician's experience, unlike some medical scales that are based on particular traits, like the Glasgow Coma Scale, where the numerical result reflects physical parameters like response to stimuli.
Two separate scales fall within the umbrella of the Clinical Global Impression. The first is an assessment before starting treatment, with a score of between one and seven. Patients with a one show no signs of mental illness, while patients scoring a seven have severe mental illness, leading to significant impairments. The doctor can make the determination on the basis of meeting with the patient, observing symptoms, and talking to people around the patient to collect more information. A patient with mild depression might score a two, while a patient experiencing psychosis might be a six.
The second scale measures response to treatment, also on a seven-point scale. Under this Clinical Global Impression, doctors determine whether patients are responding very well to treatment, scoring a one, to not responding at all, scoring a seven. Many patients fall somewhere between these two extremes. Treatment can include medications, talk therapy, dietary changes, and other measures, depending on the patient. The doctor may periodically repeat the scale to assess long-term response to treatment and determine if a patient's treatment plan is still effective for her needs.
This measure provides a thumbnail overview of a patient's situation. The Clinical Global Impression is not a diagnosis or formal evaluation of a patient, but a quick assessment. Physicians still need to meet with patients for a more in-depth evaluation. Interventions may include referring patients to specialists, adjusting medication dosages, or working with friends and family to improve the support network for the patient.
A patient may receive different Clinical Global Impression scores from different practitioners, illustrating the subjective nature of the scale. A doctor with more experience in severe mental illness might tend to scale patients more lightly, for example, thinking about serious cases she encounters. Conversely, a psychiatrist with limited clinical experiences might turn out an artificially high score because he has no basis for comparison.