性功能障礙可能有多種多樣的發病原因。它們可以粗略地分成生理的和心理的發病原因。可是，這樣的劃分常常是武斷的，因為這兩類發病原因通常是相互關聯的。而且，十分常見的是，恰恰並不是就只有一個人有性功能障礙。它是性伴雙方的一個問題。

1. 生理原因
某些男女由於受到他們身體狀況的局限，也就是由於殘障、疾病或外傷等的原因，限制了他們的性表達(sexual expression)。

2. 心理原因
也有一些生理上健康的個體，他們要麼暫時、要麼永久性地不能圓滿地享受性交生活，因為他們的性反應已經衰弱、他們的性格內向而拘謹，甚或完全因為心理的原因被阻斷。

3. 發病原因的相互關聯關係
在性功能障礙的生理和心理原因之間做出截然的劃分，在一定程度上是武斷的。當性反應發生的時候，軀體與心理是如此地相互關聯，以致於不可能在這兩者之間劃上一道清晰的分界線。毋容置疑，生理原因對一個人的心理狀態具有影響，反過來也是這樣。因而，十分常見的是，軀體與精神在形成特定性功能障礙的過程中相互產生影響。

4. 非個體的原因，而是性伴雙方的原因
要給任何一個個體診斷成性功能障礙可能是過於簡單化了，因為，通常的情形是，性功能只在涉及到另一個人時才會顯現。確實如此，在許多病例，在兩個人之間討論不協調的性關係也許會更為有益。至少，現今的性治療師要採取治療措施，經常假設單獨個體的性功能障礙要少於性伴雙方合併有的性功能障礙。因此，他們堅決要求一起治療性伴雙方。

Sexual dysfunctions can have a variety of causes. These can be roughly divided into physical and psychological causes. However, such a division is often arbitrary since the two kinds of causes are usually interrelated. Furthermore, very often it is not so much the individual, who has the problem. Instead, it is a problem of the couple.

1. Physical causes
Some females and males are restricted in their sexual expression by their physical condition, i.e. by disabilities, diseases, or injuries.

2. Psychological causes
There are also physically healthy individuals who, either temporarily or permanently, cannot fully enjoy sexual intercourse because their sexual responses have become weakened, inhibited, or even completely blocked for psychological reasons.

3. Interrelation of causes
The distinction between physical and psychological causes of sexual dysfunction is, to a certain extent, arbitrary. When it comes to sexual responses, body and mind are so closely interrelated that a sharp dividing line between them cannot be drawn. Even clearly physical causes have an influence on a person's psychological state and vice versa. Thus, very often, body and mind interact in shaping a particular sexual dysfunction.

4. Not always the individual, but often the couple
It may be an oversimplification to speak of a sexual dysfunction in any individual, because, as a rule, it manifests itself only in relation to another person. Indeed, in many cases it may be more useful to speak of an inadequate sexual relationship between two people. At any rate, sex therapists today often act on the assumption that it is less the individual than the couple who has a problem. Consequently, they insist on treating both partners together.