Generalized anxiety disorder
Anxiety of other types: Social anxiety d/o, phobias, Separation anxiety disorder, etc.
Panic disorder
Alcoholism; Alcohol withdrawal
Medication or substance abuse, e.g., caffeine, nicotine, albuterol, levothyroxine, decongestants (e.g. pseudoephedrine),
Medication or substance withdrawal, e.g., alcohol, benzodiazepines, opioids, antidepressants
Illicit drug use: Cannabis use; Cannabis use disorder; cocaine, amphetamines; Hallucinogens, etc.
Hypoglycemia
Hyperthyroidism; thyrotoxicosis
Hyperparathyroidism
Pheochromocytoma
Carcinoid
Anemia
Heart: Arrhythmia (e.g. SVTs, etc), CAD (ACS, stable angina)
Lungs: obstructive pulmonary diseases, Asthma, ARDS,
Major depressive disorder (with psychomotor agitation)
Persistent depressive disorder (dysthymia)
Adjustment disorder
Posttraumatic stress disorder (PTSD)
Attention Deficit Hyperactivity Disorder
Somatoform disorder (e.g., somatization)
Hypochondriasis
Bipolar disorder; Schizoaffective d/o; Schizophrenia
Obsessive-compulsive disorder
Serotonin syndrome
Paraneoplastic syndrome
Pulmonary embolus
Postconcussion syndrome
Temporal lobe epilepsy
Transient ischemic attacks
Multiple sclerosis
Restless legs syndrome
Hypoxemia
Electrolyte imbalance; Hypercalcemia,
Delirium
Domestic abuse
Ehlers Danlos (Hypermobility syndrome)
Wilson disease.
Malingering
Sleep disorder
Thinking over the differential diagnosis
The ddx may be divided into categories according to the mechanism of disease as follows: Psychiatric disorders, Endocrine, Cardiopulmonary, Neurologic, Substance use/withdrawal, etc.
Further Reading
DSM-5, American Psychiatric Association.
Am Fam Physician. 2015 May 1;91(9):617-624. Diagnosis and Management of Generalized Anxiety Disorder and Panic Disorder in Adults https://www.aafp.org/afp/2015/0501/p617.html
BMC Psychiatry. 2014; 14: 136. A positive association between anxiety disorders and cannabis use or cannabis use disorders in the general population- a meta-analysis of 31 studies. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4032500/