When thinking of a topic and a thesis for a cause and effect essay, it's important to keep in mind that every effect is also a cause of another effect. For example, the tilt of the earth is caused by a number of gravitational effects, but the tilt of the earth itself also causes seasonal effects on earth. For this reason, you might be assigned an essay explaining either the causes of one effect or the effects of one cause. For the sake of brevity and focus, you'll end up ignoring most of the complex web of events that make up every event. Instead, you'll focus on the immediate causes of an event or the immediate effects of an event. Since cause and effect essays may look at either a cause or an effect, it would be more accurate, and probably more helpful, to think of them as cause-effect essays, with the dash in "cause-effect" acting as a kind of bridge in both directions.
Given the infinite number of potential effects of every cause and causes of every effect, it's wise to focus on just a few causes or effects when writing a cause-effect essay. By offering a structure in which to limit your focus to a manageable scope, the traditional five paragraph essay offers a useful model for constructing your cause-effect logic. Whatever your paper's target length, the basic logic of the five paragraph essay applies. Like all essays, the cause-effect essay contains a thesis statement or a hypothesis and supporting evidence. The topic sentence of each paragraph is a statement of one particular cause-effect relationship, and each topic paragraph offers support to justify your claim that the cause-effect relationship you're describing actually exists. In a five paragraph "cause-effect" essay, the topic sentences of a five paragraph essay will offer three reasons why a particular outcome happened. In the reverse direction, a five paragraph "effect-cause" essay will describe three major outcomes of a particular event.
Depending upon the length of your paper, you may choose to write a short five paragraph essay about a causal relationship or a longer essay explaining more than three cause-effect relationships. For a freshman English paper, three causes or effects are usually sufficient to fill four to five pages if the evidence is explained sufficiently. Ideally, papers later in your career will examine far more effects and causes, resulting in more supporting paragraphs and topic sentences and, as a result, more pages.