Yes, they can. Many people end up receiving psychiatric medications and other treatments when undiagnosed and untreated medical conditions are the true cause of their so-called mental illnesses.
Dr. Ronald J Diamond is a Professor in the Dept. of Psychiatry at the Univ. of Wisconsin School of Medicine and Public Health. He’s also Medical Director of the Mental Health Center of Dane County and serves as a Consultant to the Wisconsin Bureau of Mental Health and Substance Abuse.
He’s worked over 30 years with community based treatment of persons with severe, persistent mental illness and has written clear messages to his peers stating that overlooked physical conditions are very often the source of the mental symptoms of patients.
He writes, “Every time a patient comes into your office, your emergency room or your hospital, there is a very real possibility that what seems to be a psychological problem is caused by some physical illness.”
For example, an under active thyroid gland may lead to symptoms of depression. Someone with panic attacks could have a tumor that excretes too much epinephrine (adrenaline). Or a brain tumor could cause someone to become so irritable that their personality change is leading then towards a marital breakup and they are given a psychiatric drug instead of medical care.
Dr. Diamond cites many studies involving detailed physical exams on those receiving psychiatric care which show the per cent of cases where the psychiatric symptoms were  caused by untreated medical conditions ranges from 10% to as high as 39%.
For those in the mental health profession prone to go straight to a prescription for a psychiatric drug, he has this advice:
“The most common problem, however, is that we do not think about the possibility of medical illness and, therefore, we do not specifically look for medical illness. IF YOU DO NOT LOOK FOR IT, YOU WILL NOT FIND IT.”
Mental health practitioners, family and the person himself should always consider the possibility of organic disease and explore that first.
Dr. Diamond has written a paper entitled “Psychiatric Presentations of Medical Illness-An Introduction for Non-Medical Mental Health Professionals” which gives instructions to mental health workers not trained as MD’s that shows them how to observe behaviors and symptoms that are caused by medical conditions and when to order more physical tests on a patient prior to psychiatric treatments.
Here are some important factors that indicate a medical illness could be present

• a patient over 40 with no previous psychiatric history suddenly has symptoms
• a history of head injury
• a change in headache pattern
• visual disturbances, either double vision or partial visual loss
• speech deficits
• abnormal blood pressure, pulse, temperature
• disorientation and/or memory impairment
• fluctuating or impaired level of consciousness
• abnormal body movements
• significant weight change, gain or loss
• hallucinations that are visual and vivid in color, that change rapidly
• olfactory (smell) hallucinations
• illusions: misinterpretations of stimuli
• frequent urination, increased thirst (possible symptoms of diabetes)

Sometimes medical emergencies cause a patient to arrive at a hospital emergency room with mental symptoms that are in fact caused by an acute medical condition.
These could be delirium caused by low blood sugar or very high blood sugar, unusual behavior caused by acute vitamin B-6 deficiency most often found in alcoholics when the brain is actually getting damaged, hallucinations caused by withdrawal from drugs or alcohol and acting delirious and “mad as a hatter” from an overdose of over the counter drugs or anti-depressants.
There are specific illnesses that can manifest themselves just like psychosis in some cases. Included are multiple sclerosis, Alzheimer’s disease, Encephalitis (viral infection of the brain, syphilis of the central nervous system, HIV infections and AIDS. Or the patient might have a brain tumor, brain abscess or bleeding within the skull.
Additional types of medical problems include disorders in metabolism, nutritional deficiencies and endocrine disorders. All of these categories can create behavior that appears to be a mental condition when it is a physical one.
And, of course, there is a large variety of psychiatric drugs, prescription drugs and street drugs that worsen mental stability and create psychosis on a temporary or longer term basis. Dr. Diamond, to his credit, is not afraid to list these out for his fellow psychiatrists and mental health workers to consider before trying to “help” a patient with more drugs.
It’s quite clear today that the first step of any “mental health diagnosis” should be a complete medical exam that looks thoroughly to discover any untreated illnesses and physical injuries. These repaired the patient is often no longer a patient but has returned to his normal state of mind and is actively getting on with his life.
No psychiatric treatment needed.
http://www.alternativementalhealth.com/articles/diamond.htm