What was wrong with Betty's hands?

You are correct in both your assertions that we never find out exactly what is causing Betty's shaky hands, and that we know based on evidence that it is likely psychological.

As you mention in your question, the shaky hands are a part of Betty's character from day one. The first observance of this problem by the viewer is roughly three months after her mother dies (by Betty's own admission at her first visit to the psychiatrist). The issue is forced in "Ladies Room" (S1E2) after two hand-shaking incidents (the first was following a night of heavy drinking, the second when Betty's hands freeze up while driving sending the car up a curb) Betty is encouraged by her doctor to see a psychiatrist, as he believes the problem could be psychological.

At the conclusion of "Ladies Room," we observe Don listening to the psychiatrist's report on Betty's visit, and then nothing. After this episode, the writers leave the viewer to draw his or her own conclusions. Betty's shaking hands largely stop. But in the S2E3 ("The Benefactor"), Betty is hit on by a married man while at a horse stable, and in the process of lighting her cigarette while rebuffing his advances, we see her shaky hands return.

In summation;

• No, we do not find out precisely what causes Betty's shaky hands,
• Yes, it likely is psychological based on circumstantial evidence,
• No, there is no overwhelming evidence that there is something physically wrong with Betty.

<sup>Sources:
- "Sexism Makes Me Hate Betty Draper"
- Mad Men Wikia</sup>

It could be a thyroid thing too, Betty was diagnosed and treated in a later season. With over and under active thyroid disorders you can have shaky hands off and on, numbness in certain body part too. Back then it was nearly impossible to catch it, the sad thing is it's still nearly impossible to catch it.

Betty's hands were shaking because she was repressing her feelings. Notice that Betty was unhappy being a housewife. Also notice that she never talked about her problems with Don. When he asked her if she was unhappy, she lied and said no straight to his face. Don also has this problem but instead if repressing it, he sees his mistress. Betty's hands stop shaking because she starts voicing her opinions more after she finds out that Don has being cheating on her with Bobbie. I thought her hands woul start shaking again when her father dies but instead she tarts having an affair with Henry to deal with it. I hope this makes sense.

Betty Friedan's book was a bestseller then, describing the dull empty ache and deep dissatisfaction so-called happy housewives suffered. They're not allowed to voice it. They can't even identify it to themselves. So it manifests in idiopathic ways like shaking and numbness.

Post-war 1950s-60s married women had 'everything,' so what's the problem? Whether their college degrees were professional- or Mrs-bound, women were rendered merely 'helpmates' to their husbands they should feel so lucky to have 'landed.' It would be unthinkable to have a life or even opinions of their own. There was nowhere for an unspeakable feeling of anxiety and loss of identity to go, so Betty's hands went numb.

Carpal tunnel. She is nauseated and having hand cramping. She is pregnant. Ends up knowing later. Over 50% women get carpal tunnel during pregnancy.