Johnson had several health problems, including childhood tuberculous scrofula resulting in deep facial scarring, deafness in one ear and blindness in one eye, gout, testicular cancer, and a stroke in his final year that left him unable to speak; his autopsy indicated that he had pulmonary fibrosis along with cardiac failure probably due to hypertension, a condition then unknown.
Johnson displayed signs consistent with several diagnoses, including depression and Tourette syndrome.

There are many accounts of Johnson suffering from bouts of depression and what Johnson thought might be madness.
As Walter Jackson Bate puts it, "one of the ironies of literary history is that its most compelling and authoritative symbol of common sense—of the strong, imaginative grasp of concrete reality—should have begun his adult life, at the age of twenty, in a state of such intense anxiety and bewildered despair that, at least from his own point of view, it seemed the onset of actual insanity".
To overcome these feelings, Johnson tried to constantly involve himself with various activities, but this did not seem to help.
Taylor said that Johnson "at one time strongly entertained thoughts of suicide".
Boswell claimed that Johnson "felt himself overwhelmed with an horrible melancholia, with perpetual irritation, fretfulness, and impatience; and with a dejection, gloom, and despair, which made existence misery".

Early on, when Johnson was unable to pay off his debts, he began to work with professional writers and identified his own situation with theirs.
During this time, Johnson witnessed Christopher Smart's decline into "penury and the madhouse", and feared that he might share the same fate.
Hester Thrale Piozzi claimed, in a discussion on Smart's mental state, that Johnson was her "friend who feared an apple should intoxicate him".
To her, what separated Johnson from others who were placed in asylums for madness—like Christopher Smart—was his ability to keep his concerns and emotions to himself.

Two hundred years after Johnson's death, the posthumous diagnosis of Tourette syndrome became widely accepted.
The condition was unknown during Johnson's lifetime, but Boswell describes Johnson displaying signs of Tourette syndrome, including tics and other involuntary movements.
According to Boswell "he commonly held his head to one side ... moving his body backwards and forwards, and rubbing his left knee in the same direction, with the palm of his hand ... [H]e made various sounds" like "a half whistle" or "as if clucking like a hen", and "... all this accompanied sometimes with a thoughtful look, but more frequently with a smile.
Generally when he had concluded a period, in the course of a dispute, by which time he was a good deal exhausted by violence and vociferation, he used to blow out his breath like a whale."
There are many similar accounts; in particular, Johnson was said to "perform his gesticulations" at the threshold of a house or in doorways.
When asked by a little girl why he made such noises and acted in that way, Johnson responded: "From bad habit."
The diagnosis of the syndrome was first made in a 1967 report, and Tourette syndrome researcher Arthur K. Shapiro described Johnson as "the most notable example of a successful adaptation to life despite the liability of Tourette syndrome".
Details provided by the writings of Boswell, Hester Thrale, and others reinforce the diagnosis, with one paper concluding:
[Johnson] also displayed many of the obsessional-compulsive traits and rituals which are associated with this syndrome ... It may be thought that without this illness Dr Johnson's remarkable literary achievements, the great dictionary, his philosophical deliberations and his conversations may never have happened; and Boswell, the author of the greatest of biographies would have been unknown.
Johnson had several health problems, including childhood tuberculous scrofula resulting in deep facial scarring, deafness in one ear and blindness in one eye, gout, testicular cancer, and a stroke in his final year that left him unable to speak; his autopsy indicated that he had pulmonary fibrosis along with cardiac failure probably due to hypertension, a condition then unknown. Johnson displayed signs consistent with several diagnoses, including depression and Tourette syndrome.
There are many accounts of Johnson suffering from bouts of depression and what Johnson thought might be madness. As Walter Jackson Bate puts it, "one of the ironies of literary history is that its most compelling and authoritative symbol of common sense—of the strong, imaginative grasp of concrete reality—should have begun his adult life, at the age of twenty, in a state of such intense anxiety and bewildered despair that, at least from his own point of view, it seemed the onset of actual insanity". To overcome these feelings, Johnson tried to constantly involve himself with various activities, but this did not seem to help. Taylor said that Johnson "at one time strongly entertained thoughts of suicide". Boswell claimed that Johnson "felt himself overwhelmed with an horrible melancholia, with perpetual irritation, fretfulness, and impatience; and with a dejection, gloom, and despair, which made existence misery".
Early on, when Johnson was unable to pay off his debts, he began to work with professional writers and identified his own situation with theirs. During this time, Johnson witnessed Christopher Smart's decline into "penury and the madhouse", and feared that he might share the same fate. Hester Thrale Piozzi claimed, in a discussion on Smart's mental state, that Johnson was her "friend who feared an apple should intoxicate him". To her, what separated Johnson from others who were placed in asylums for madness—like Christopher Smart—was his ability to keep his concerns and emotions to himself.
Two hundred years after Johnson's death, the posthumous diagnosis of Tourette syndrome became widely accepted. The condition was unknown during Johnson's lifetime, but Boswell describes Johnson displaying signs of Tourette syndrome, including tics and other involuntary movements. According to Boswell "he commonly held his head to one side ... moving his body backwards and forwards, and rubbing his left knee in the same direction, with the palm of his hand ... [H]e made various sounds" like "a half whistle" or "as if clucking like a hen", and "... all this accompanied sometimes with a thoughtful look, but more frequently with a smile. Generally when he had concluded a period, in the course of a dispute, by which time he was a good deal exhausted by violence and vociferation, he used to blow out his breath like a whale." There are many similar accounts; in particular, Johnson was said to "perform his gesticulations" at the threshold of a house or in doorways. When asked by a little girl why he made such noises and acted in that way, Johnson responded: "From bad habit." The diagnosis of the syndrome was first made in a 1967 report, and Tourette syndrome researcher Arthur K. Shapiro described Johnson as "the most notable example of a successful adaptation to life despite the liability of Tourette syndrome". Details provided by the writings of Boswell, Hester Thrale, and others reinforce the diagnosis, with one paper concluding:
[Johnson] also displayed many of the obsessional-compulsive traits and rituals which are associated with this syndrome ... It may be thought that without this illness Dr Johnson's remarkable literary achievements, the great dictionary, his philosophical deliberations and his conversations may never have happened; and Boswell, the author of the greatest of biographies would have been unknown.
Samuel Johnson